London's terror protocols: The plan for the next 7/7

She is a piebald border collie called Shelley, seven years old, and she wears a jingling harness mounted with bells and lights. She is trained to follow human scent, and there are people down in this cramped and dusty hole, though none are in a good way. A man lies supine among broken breezeblocks and sandbags with massive crush injuries to his chest. The prone woman next to him is dead already, both her hands taken roughly off by the same explosion. Another benighted individual sits grubby and stained with an exposed compound fracture on his right arm, cradling a child. A further infant is close, in the throes of an acute asthma attack. All is dusty. All is dark. The dog trots out. Some time later the first voice comes. It is a strong voice.

"Right, hello, can you hear me? Fire brigade. Can anybody hear me down there?"

"Yep, ep, ep." The man with the compound fracture moans incoherently.

Two firefighters in red overalls clamber into the confined space. They are Mark Ryan and Pete Thompson, both based in South London. One tries to prise the child from the whimpering man with the ruined arm. The man resists. "No speak," he insists. He holds tight until the fireman lifts his injured arm and the movement of the exposed bone is too much for him. He lets the child go.

Two paramedics arrive, crawling into the same narrow space in their green uniforms. Amid the squawk of their radios, Jenna Davis and Terry Longhurst, members of a London Ambulance Service Hazardous Area Response Team (HART), get to work. They assess the human wreckage and administer salbutamol to ease the second child's breathing difficulties.

London prepares for the worst

It is not for real. Most of the bodies are limp dummies, smeared with fake blood and with chicken soup standing in for vomit. The man with the simulated compound fracture is real enough, though actually a 53-year-old former Welsh miner called Dai Ford rather than an immigrant with limited grasp of English. Nor is the location London, rather the Rhondda Valley of South Wales, a geological trench scarred with more than 75 coal works. The mines have closed now, but the mine rescue training centre, opened by King George V in 1912, still stands in the village of Tonypandy, its white walls containing claustrophobic mock-ups of labyrinthine underground passages.

Nevertheless, despite being some 160 miles from Trafalgar Square, this training exercise focuses firmly on the British capital. The firemen come from the London Brigade's Urban Search and Rescue (USAR) teams, established after the 9/11 attacks in the US to extract survivors from similar piles of smoking rubble. The Ambulance Service's HART teams came into being after the 7 July 2005 bomb attacks on the London Underground in order to provide clinical care in difficult, potentially contaminated environments. Ten years ago the paramedics did not have the equipment, notably the requisite breathing apparatus, to venture into the smoke-filled Tube tunnels after the attack.

This exercise in far-off Wales is part of the multifaceted way in which London, a city spread across 607 square miles and home to upwards of eight million people and much of the architecture of the global financial system, prepares for the worst. This story is one of doomsaying, of making provision for the unpalatable or the unthinkable. It is partly operational, a saga of how various pieces, from armed police to ambulances, would move on the great real-life Monopoly board of the British capital if a terrorist attack or other major disaster took place. But this story also traverses more conceptual terrain. To examine how London prepares for the worst is to observe the balancing act of urban resilience. Robustness always comes at a cost, both fiscally and in knock-ons for other elements of society. Above all, there is always the danger of planning for the last disaster, rather than the one to come.

'All these other threats'

The current thinking regarding emergency planning in the UK is rooted in a period of considerable public disturbance that took place around the turn of the millennium. In short order the government of Tony Blair faced an outbreak of foot and mouth disease, flooding, fuel protests and firefighters' strikes, a maelstrom those in government christened the "Four Fs".

Blair's administration decided that a new institution and a revised legal framework were required. In July 2001, the Cabinet Office created the Civil Contingencies Secretariat, whose task it is to prepare for catastrophe. The Civil Contingencies Act, conceived before 9/11, eventually passed into law in 2004. Four years later, in 2008, the government for the first time published a national risk register, a document outlining the threats faced by the UK.

"It was about a move away from terrorism to look at all these other threats – things like serious disease outbreak, civil unrest, severe weather events," says Jennifer Cole, a senior research fellow at London's Royal United Services Institute focusing on emergency management and resilience. "How did we make ourselves resilient to those, which was not just a police response, because there wasn't necessarily a bad guy to catch."

The latest version of the register, the public version of a classified equivalent, was published in March this year and contains two matrices, the first examining "Risks of Terrorist or other malicious attacks", the second "Other Risks". The position of individual events on the grids plots the "overall relative impact score" against "relative plausibility of occurring in the next five years".

The six events on the terrorism matrix range from "catastrophic terrorist attack" (relative impact: five, the highest on the scale; relative plausibility: two) to "cyber attacks: infrastructure" (impact: three; plausibility: two) and "attacks on transport systems" (impact: three, plausibility: five). For other, non-terrorist, risks the matrix gives actual probabilities. Pandemic flu, the most devastating of these, is put at a probability of between 1/20 and ½ in the next five years. Inland flooding and major industrial accidents, both with an impact of three on the five-point scale, sit at between 1/200 and 1/20, and between 1/2,000 and 1/200, respectively.

But the terrorism to which the government must respond has also continued to evolve. From the 1970s to the 1990s, in the high period of Irish Republican violence, the UK in general and London in particular faced a bombing campaign. However, the Provisional Irish Republican Army would often call in a warning before detonation, allowing the evacuation of the target, or set devices to blow up at night when offices were empty. The 1993 Bishopsgate bombing, when one tonne of explosive made from ammonium nitrate and fuel oil exploded in the financial district of the City of London, caused £350m in damage but killed only one person.

After 9/11 the focus shifted to Islamist suicide attacks, which reached their UK apogee (at least so far) in 2005 with the Tube strikes. In 2008 the trend shifted again. In November that year 10 Pakistani members of Islamic militant organisation Laskhkar-e-Taiba ran amok in Mumbai, India's most populous city. A combination of 12 bombing and shooting attacks over several days left more than 160 people dead and at least 308 injured.

In the aftermath, security forces worldwide increased the attention they paid to the risk of a "marauding terrorist firearms attack" (MTFA), in essence a gunman or gunmen on the loose, potentially armed with rapid-firing automatic weapons (the Mumbai gunmen were armed with AK-47s.) This fear was cemented in January this year when two French-Algerian brothers, Saïd and Chérif Kouachi, attacked the Paris office of Charlie Hebdo, the belligerent French satirical magazine that had published cartoons of the prophet Mohammed, and further reinforced last week when a 22-year-old gunman opened fire on tourists in Tunisia.

Eleven people died at the Charlie Hebdo offices on January 7. A further five were killed in related attacks in the region around Paris. The subsequent manhunt reached its dénouement in a shootout on an industrial estate at Dammartin-en-Goële, 35 kilometres northeast of the capital, on January 9. The French authorities mobilised 88,000 responders from the police and other security forces, all of whom were armed.

Since January the discrepancy between the French response to Charlie Hebdo and the level of police firearms provision in the UK has stirred controversy in law enforcement circles. Almost uniquely worldwide (Norway, Iceland, Ireland and New Zealand are the other exceptions), regular British police do not carry guns. Police forces in England and Wales have around 7,000 armed officers, of whom 2,127 are in London (total police officer numbers in England and Wales stood at 127,909 in March 2014). The majority of armed officers serve as "Armed Response Vehicle Officers", riding in pairs or threes in vehicles - often BMW X5s - with pistols on hand and carbines in the boot. A smaller number are "Specialist Firearms Officers", trained in hostage rescue and advanced counter-terrorism techniques.

Recent police cuts, part of the wider UK government austerity plan, have placed considerable pressure on firearms provision. Simon Chesterman, the Association of Chief Police Officers' lead authority on armed policing, turned down a request to be interviewed for this article, citing the security implications of discussing anti-terror plans. However, writing in Top Cover, the journal of the Police Firearms Officers Association, after the Charlie Hebdo attack, he said that while he was "confident we could respond to the sieges" in a similar incident in the UK, the follow-up if the attackers escaped would be another matter.

"The prospect of a nationwide manhunt for armed terrorists who have gone to ground after carrying out an attack is deeply concerning," he wrote. "It is the potential for a series of no-notice attacks, not to mention the request to respond to positive and false sightings, that would significantly stretch our armed resources and very quickly we would be seeking military support to help with cordons and searching."

Steve White, the chair of the Police Federation of England and Wales, and a former firearms officer himself, adds that, since recent cuts, individual firearms officers are in such demand that they are unable to take their allowances of leave.

"We've lost 17,000 police officers," he said. "You can't take nine forces out of the 43, which is the equivalent of what has been lost, and have it not to impact on stuff like public disorder, national co-ordination, firearms capability."

The 'dirty bomb'

The second type of terrorist scenario much discussed in the post-9/11 period was that of a "dirty bomb", or radiological device, which does not achieve fission or fusion but uses explosive to disperse radioactive material. Assessments of the likelihood and impact of such an attack vary. Sceptics say dirty bombs are unlikely due to the complexity of obtaining the required material and the perils of construction. "Drumming up unrealistic fear over dirty bombs is a way of ensuring that more likely, but lower-level radiological threats are kept on the agenda", says Jennifer Cole of RUSI. "Dirty bombs would be difficult to construct, difficult to deliver, and arguably would not cause significantly more, or more serious, damage than a conventional explosive – the real harm is more likely to be the economic disruption caused by the need for the specialist clean-up operation and the fear surrounding anything involving radiological material due to lack of understanding of the science. A radiological dispersion device, which releases radiation naturally, without the need for an explosion, or a radiological poisoning incident such as the one that killed Alexander Litvinenko is more likely, but much smaller scale than the science-fiction scenarios usually cited."

On the other side of the debate, Daniel Percival, a filmmaker who in 2004 produced a docudrama, Dirty War, about a radiological attack on London, suggests that the possibility of a dirty bomb, along with chemical, biological or even nuclear terrorism, is "increasing all the time".

"The technology is incredibly simple now," he says. "One of the arguments against nuclear technology was that it was inaccessible and difficult and had to be in the hands of rogue states. That's not actually true, nuclear technology and radiological technology are very accessible." "Fissile technology," he adds, "is 60 years old."

A radiological strike, or a more prosaic but potentially equally hazardous event such as a toxic chemical spill, would necessitate "mass decontamination", in essence stripping those affected and hosing them down. For small numbers, decontamination, as a "clinical intervention", is the preserve of the ambulance service. If numbers are too great for paramedics to handle, it becomes the preserve of the fire brigade, which in 2004 began to acquire specialist equipment as part of a post-9/11 procurement programme called "New Dimension".

London now has ten mass-decontamination "incident response units", large lorries equipped with collapsible tents. People enter the front, disrobe, and pass through a showering
area where they can be scrubbed down, before entering a "rerobing" area where they are given temporary clothing. Each unit can process 200 people per hour, and there are provisions to bring in additional units from elsewhere in the UK if the 10 in London are insufficient.

"We're the lead in terms of decontamination if the ambulance service are overstretched," explains Fire Brigade Commissioner Ron Dobson. "Theirs is much more clinical than ours; ours is more of a blunt instrument."

Sally Leivesley, a security consultant focusing on "catastrophic and extreme risk", suggests that in the case of a really large-scale incident the fire brigade might use even more rudimentary decontamination procedures to cope with the numbers. "There's theory and then there's reality," she says. "They wouldn't necessarily go through the very tortuous process of decontamination that we've seen in the official filming of it... if you want to decontaminate people you might walk them under two fire hoses between two pumps."

In the most extreme cases plans exist to move large numbers of people out of London. Those plans have not always been kept safe. In 2004 the Metropolitan police launched an inquiry after a warehouse worker found four CD-Roms on a commuter train between London and Gravesend in Kent, one of which contained traffic management plans for "Operation Sassoon", a mass evacuation of the capital.

The Ambulance Service has been preparing for a chemical, biological, radiological or nuclear (CBRN) incident since the late Nineties, following the Tokyo subway attacks of March 1995. Doomsday sect Aum Shinrikyo released the nerve agent sarin in five co-ordinated attacks, killing 12 people and injuring more than a thousand. The London Service now has the HART teams instituted after the 7/7 bombings to respond to CBRN threats, and one spring weekday in April I visited the secret site on the western outskirts of London where one of the city's two six-strong teams is based.

Simon Woodmore, the HART operations officer for west London, took me through a hangar-like building where its specialist equipment was laid out on show. We passed several types of gas-tight suits, some with powered filters, others with their own self-contained air supplies, the "personal protective equipment" set-up of boots, mask, and goggles developed for British responders to Ebola, a buggy-like six-wheeled off-road vehicle and even body armour in Ambulance Service green.

Woodmore explained that the objective was to provide clinical care inside the "hotzone", be that a chemically or radiologically contaminated area, or, in a marauding firearms incident, in an area thought to be cleared but where a shooter could still be at large (the "warmzone"). HART, said Woodmore, means the ambulance service is no longer dependent on "fire colleagues taking people from the hotzone." He added: "Post the 7 July bombings it was seen that the ambulance response and the clinical response needed to be in the hotzone, that point of release."

London's Mass Fatality Plan

Emergency planners emphasise that the actual nature or direct cause of an incident is less important than one might expect when it comes to organising the response. Regardless of whether the cause is a terrorist bomb blast, a train crash or even a flood, many of the subsequent activities are same: authorities need to cordon off danger areas, arrange for the triage and treatment of casualties and communicate the situation clearly to the public.

In the most serious incidents one of the most important functions is handling the dead, potentially in large numbers. At the Welsh training exercise, two women in orange one-piece jumpsuits, accompanied by a photographer, followed the fire brigade's USAR teams through their drills. The scenario was a gas explosion in a building that turned out to be in use by an illegal people-smuggling operation. These women in orange were disaster victim identification (DVI) technicians from the Metropolitan and City of London Police. When they encountered a cadaver – played here by a dummy, and already tagged by the first responders with a laminated black triage sleeve bearing the capitalised word "DEAD" – they performed an elaborate procedure called a "forensic recovery". One technician – holding a clipboard and detailed as "clean" – ie. free from potential contamination by blood or other body fluids – acted as the scribe, noting details and all actions taken. The photographer, likewise "clean", used his camera to visually document the recovery. Meanwhile the second technician placed bags over the hand, feet and head of the "corpse" and wrapped the body in a sheet.

"Anything that's of interest forensically, potentially, is inside that sheet," explained Constable Phil Stone, the DVI co-ordinator for the Metropolitan Police. Further grey tags, stamped PM for "post-mortem", give each body – or body part in the event of dismemberment – a unique identification number. These tags also bear the UK international dialling code of +44 to identify nationality in an incident – such as a plane crash – where victims could come from a multitude of countries. Once body parts have reached a mortuary, officers identify the dead by cross referencing "primary identification factors" – DNA, teeth and fingerprints – and secondary factors – such as clothing, jewellery or scars – with information provided to family liaison officers.

Overall, across the Metropolitan Police, the City of London Police and the British Transport Police, the capital has around 250 trained DVI technicians. In a major incident they operate in teams of six: a typical set up would see a team leader, who serves as scribe, managing a photographer, two recovery officers to handle the dead and two safety officers to look after them.

"You get very tied up in the task you're doing," Stone explains. "It's just somebody to stand back and say 'mind your head on that' or 'be careful on that bit'." London has six "refrigerated storage units" – mobile cubes that can each keep 12 bodies cold to prevent putrefaction. Across the UK around another 20 are available and, as with decontamination equipment, plans exist to move them to the capital if needed.

In the event that the number of bodies is overwhelming – here pandemic flu is considered the most likely cause – London's Mass Fatality Plan also contains provisions to deploy a temporary structure or structures called the "National Emergency Mortuary Arrangements". Constructed by the American engineering firm KBR, the "NEMA" is a tented system that can be set up as one 600-body morgue or two 300-body facilities. Nine locations in London – that cannot be disclosed – are earmarked for possible NEMA use.

Although it concerns itself with the dead, disaster victim identification, as David Alexander, Professor of Risk and Disaster Reduction at University College London, says, "Is really about the living," ensuring that victims' families see their loved ones respectfully treated and feel the bureaucracy has reacted with compassion and efficiency. As the London Mass Fatality Plan states: "It is the absolute right for bereaved families to view the remains of their loved ones, subject to health and safety issues."

Flight is a wholly rational response

You have probably seen the photograph on the before. It was taken in Lower Manhattan on September 11, 2001 as a dust cloud from the falling towers billowed into a street. Pedestrians flee towards the camera. Two have their right hands aloft. At first encounter it seems you could exchange the background dust cloud for the corniest of Hollywood horrors – Godzilla, or a hoard of zombies – without requiring any adjustment to the body language and demeanour of the human participants. The photo appears to embody the classic tropes of mass panic in the face of disaster – uncontrolled emotion and selfish behaviour.

That notion would be wrong, according to Chris Cocking, a psychologist who studies crowd behaviour at the University of Brighton. Cocking uses the 9/11 photograph as a teaching aid. His first point is that, when faced with a situation that could kill you, flight is a wholly rational response. People running does not alone indicate panic. Secondly, he points to a woman in the photograph still wearing her high-heeled shoes. Again, if the situation were truly a headlong flight, she would surely have kicked them off. Finally Cocking picks out examples of co-operation between individuals in the image, notably the man in the rucksack at stage left who appears to be shouting at the photographer to get out of the way.

"Generally the idea of mass panic is a complete myth," says Cocking. "People behave much better than is often expected of them. Being in those emergencies tends to create a shared sense of identity and a shared norm of behaviour, and the shared norm is co-operation rather than selfish behaviour." Cocking's findings are underwritten by two studies he worked on with fellow psychologist John Drury on the survivors of the July 2005 attacks on London, published in the International Journal of Mass Emergencies and Disasters (2009) and in the International Journal of Emergency Services (2013).

These studies found that "spontaneous co-operation amongst survivors often emerged, and this was a function of a common identity that grew out of a sense of shared fate amongst those affected". Survivors helped themselves and each other, improvising tourniquets and other first aid measures, sometimes at considerable risk to themselves.

There is notable irony here: in daily life on a London Tube train, physical proximity is combined with almost zero social interaction. Unlike on public transport in much of the developing world, few people talk to each other or even make eye contact. Come a disaster, however, as Cocking puts it, "atomised individuals" immediately became "a psychological crowd".

"The people we interviewed on 7/7," he explains, "they said that these people next to me instantly became the most important people in my life". Cocking uses his findings to argue that emergency services should factor in the ability of survivors – whom he terms "zero responders" – to help other, more gravely afflicted people. The authorities, however, do not seem keen to add that factor to their planning. John Drury, another crowd psychiatrist at the University of Sussex, completed a study of 47 UK government emergency planning documents and found that nine referred to panic. Another common representation of the public was that they would simply behave passively, without the sharing behaviour that experimental data indicates is likely to occur.

"What's slightly problematic in that is the literature also acknowledges that in many emergencies or disasters the professionals simply won't be there," Drury says.

The authorities – in particular the blue-light services – are understandably wary of have-a-go heroes who could imperil themselves and others by interfering in crises without experience or training. Scripts given to actors playing the roles of victims in training exercises sometimes include "overreaction", the technical term for panic.

But the emergency services are not without weaknesses of their own. In emergency response circles the London Assembly Report into the July 7 bombings, published in 2006, is sometimes derided for making recommendations that seem sensible to outsiders but that professional practitioners know are simply unfeasible – the classic example is its call to stock first aid kits on Tube trains, when experience shows they are inevitably and rapidly stolen. The remarks, however, of Richard Barnes, who chaired the inquest committee, regarding the distinction between the emergency services' objectives and the actual needs of Londoners ring true:

"The relevant statutory organisations have their emergency plans in place. These plans have been tested, practised against and refined. However, the thread that links them all together is that in the event they proved service-specific, meeting the needs of the services, and lacked an outward focus that took into account the needs of their client groups." Barnes added: "Responders are dealing with individuals not an 'incident'."

The 'Blitz Spirit'

The correct way for the authorities to communicate with the public in times of crisis is in part a continuation of the assumptions about panic. The bind for the authorities is how much, or how little, information they should distribute. But beyond the old official fear that the public will lose their heads, there are a number of other problems. In the event of terrorism, authorities are understandably reluctant to give away too much information on their planned responses. Secondly, in Britain at least, the public have a pronounced tendency to ignore information they are presented with. In 2004 the government launched a campaign to send every household in the country a 22-page emergency advice booklet, which included first aid information and suggestions such as keeping supplies of tinned food, bottled water and batteries. A follow-up study found that very little of this advice was actually taken, though rural communities were somewhat more likely to follow it than their urban counterparts.

"Members of the public have so much confidence in the emergency services they think they're going to be rescued anyway, so they just won't do it," says Brooke Rogers, Reader in Risk and Terror in the Department of War Studies at King's College London.

The other factor in the psychological mix is national. The British like to believe the way they behave in a crisis is unique, that when the worst comes they are phlegmatic and co-operative, pulling together and remaining good humoured. The language is well worn – terms like "stiff upper lip" and "staunch" abound – and this national story exists in firm opposition to the perceived proclivities of other nations; the French would shout, the Italians would panic, the Americans would come over all gung-ho...

"Dunkirk Spirit" is another term frequently used, alluding to the evacuation of British soldiers – in part by civilians in small boats – from northern France in May and June 1940. That term also hints at another piece of the British national psychological jigsaw, the determination to recast grievous defeats as triumphs of pluck. London has its own version of this story: the Blitz Spirit, the idea of a doughty capital, a determined metropolis conducting "business as usual" under German bombing.

Scratch the surface though and these ideas rapidly become less convincing. In 1991, Scottish academic Angus Calder published The Myth of the Blitz, in which he examined contemporary accounts like this one from Nina Masel, a young employee of social research organisation Mass Observation, during heavy raids in September 1940: "The whole story of the last weekend has been one of unplanned hysteria. Of course the Press versions of life going on normally in the East End are grotesque. There was no bread, no electricity, no milk, no gas, no telephones... The Press version of people's smiling jollity and fun are gross exaggeration. On no previous investigation has so little humour, laughter or whistling been recorded."

The myth of the Blitz, Calder suggested, began to be constructed by British propaganda before German bombs started to fall in earnest, and it has been so enduring because it is buttressed by the "Big Truth" – the undeniable fact that Britain did eventually prevail and that overall civilian morale did not shatter. The sizeable shadow of that truth has obscured myriad smaller, but rather less heroic, actualities.

Still, the trope of London's – and Londoners' – particular and unique robustness has remained undaunted by academic research, both in the UK and much further afield. "How London carried on," wrote the Guardian after the 7/7 attacks of 2005. "London can take it, and so can the rest of the world," added the Australian publication The Age. "Spirit of the Blitz emerges amid the chaos," chimed the Irish Times. Mike Granatt, former head of the Civil Contingencies Secretariat, suggests years of IRA terrorism left Londoners "wonderfully bloody-minded" and determined to get on with life in the face of chaos.

Crowd psychologist Chris Cocking points out that similar claims about a city's unique toughness were made in New York after 9/11 and in Madrid following the March 2004 attacks on the rail system there. "It's used often as almost a propaganda device to say there's something particularly special about that city or that country," he says. "I would say it's probably a universal response."

Flames flowing up onto the street

Around lunchtime on Wednesday 1 April this year smoke began to seep from underneath an inspection cover on a broad central London street called Kingsway. Responding fire fighters discovered an electrical blaze in a Victorian tunnel beneath the road. When an eight-inch gas main ruptured, flames began to flow up onto the street.

Fire-fighters decided it was safer to leave the conflagration alight until the gas supply had been isolated – brigade commissioner Ron Dobson later used a domestic cooker as an analogy: safe if burning, dangerous if leaking unlit gas and liable to cause an explosion. Thirty-six hours passed before the fire was finally extinguished.

I arrived at the scene around nightfall and was told by newspaper distributor Hemang Vyas: "It was a bit of fire, and then everything cleared up. Round 2:30, everything was closed down." That closure was significant. Though the fire caused no casualties, and little permanent damage – and although it took place just before the Easter weekend, when commercial activity was at a relatively low ebb – the disruption was major.

Some 5,000 people were evacuated from nearby buildings, including the Royal Courts of Justice. The nearby London School of Economics activated its Major Incident Initial Response Plan, sealing its campus. Holborn Underground station closed and 10 bus routes were diverted. Shows at the nearby Lyceum, Duchess and Aldwych theatres were cancelled. UK power networks said thousands of customers in the area were left without electricity. Photographs taken that night from the London Eye Ferris wheel on the south bank show a huge swathe of normally brightly lit central London in blackout darkness.

The deputy president of the London Chamber of Commerce estimated the cost to the capital's businesses was as much as £40m. The scale of that figure – stemming from an incident limited both in scale and duration – shows the importance of a third tier of disaster response, sandwiched between the state and the individual: private firms also need to gird themselves for the unexpected.

In the 1990s wholesale back-up offices were the favoured solution for companies looking to establish contingency measures. A more refined, and cost-effective system, is "syndicated space", where providers lease serviced offices to several different firms, but agree to a certain geographical spacing between all their clients' primary locations. So if one company's headquarters is made inaccessible by fire, flood or terror attack, they can use the reserve space confident that the other clients will probably still be in their primary facilities, and not trying to move into the same back-up space.

An alternative plan is to enlist the services of a firm with such a large network that it can absorb most eventualities. The "workplace provider" Regus operates 3,000 centres in 900 cities and 120 countries. In the UK Regus has 350 facilities – totalling seven million square feet. 90 are in London. UK chief executive Richard Morris explains that with such a depth of resources they can provide back-up space in most situations. In London their workplace recovery business has seen 100% year-on-year growth over the past three years. The fee structure has two parts – a fixed retainer and a flexible amount depending how much use the company makes of its reserve locations. The retainer ranges from £150 per year per person for general business lounge access and standard IT provision to £500 per person per year for a private office suite, with more "test days" included and additional IT provision.

The fact that – even in well-heeled industries like finance – not all businesses' arrangements are created equal was vividly underwritten when Hurricane Sandy struck New York in October 2012. A photograph of the city skyline rapidly began to circulate showing Goldman Sachs headquarters at 200 West Street still lit up while much of the rest of Lower Manhattan was plunged into darkness by power outages. Goldman's building, which the bank ringed with a formidable 4.6-metre barrier of sandbags before the storm arrived, had separate generator power. Stephen Flynn, director of the Center for Resilience Studies at Boston's Northeastern University, suggests Goldman's willingness to invest in flood protection may have stemmed from the fact that the bank owns the freehold on its headquarters. Elsewhere, Citigroup's pre-Sandy protection for its own Lower Manhattan offices, which the firm rented, ran to only a desultory handful of sandbags. Citigroup's building duly flooded.

The real death of cities

Overall, Britain's emergency plans are robust, enormously so when compared with those of developing countries. One government employee, speaking off the record, pointed to a tiny club of other nations – Germany, possibly France, the US who – "could actually cope with it". And although a disaster might kill many of its citizens, it is unlikely that anything short of a thermonuclear bomb would kill the city itself – or at least, that it would do so all at once.

Cities do not die so quickly. Just look at New Orleans after the arrival of Hurricane Katrina in August 2005. Some 80% of the city flooded and the police abandoned search and rescue missions to control widespread looting. During the ten months that followed, the loss in wages was approximately $2.9bn, with 76% in the private sector. At least 1,833 people died in the hurricane and total property damage was estimated at upwards of $100bn. After Katrina and Rita, the storm that followed, the Federal Emergency Management Agency provided temporary housing to more than 143,000 families.

Although New Orleans did not fully expire, and has made significant progress towards recovery, its fate still suggests the impact that a sudden "no-notice" event can have on a city.

On closer examination though, that narrative does not really stand up. The chaos after Katrina revealed long-running dysfunction and racial tension within the city's administration, but the disaster itself was also, in the view of Richard Campanella, a geographer at New Orleans' Tulane University, in part the result of a hundred year bet that the city had made against its own environment, the Mississippi River Delta.

Starting in the 18th century, authorities began to construct levees, embankments to prevent the overflow of the river and flooding of the low ground. The levees stopped regular flooding, but they also prevented the deposition of fresh sediment to make up for that washed out to sea and, by drying out the land, caused it to contract and sink further – a process exacerbated by municipal drainage in metro New Orleans, half of which subsequently sunk below sea level.

"Ground level falls below the level of the sea and the reason why the sea doesn't pour into it is because we've erected these levees around it," Campanella explains. "So you have this rather unusual circumstance of an anthropogenically sinking city surrounded by an anthropogenically raised rim, so you have a sinking bowl" by the hand of man.

Simultaneously an expanding network of canals between the city and the sea allowed rising seawater to intrude, speeding up erosion. Since the 1930s Louisiana has lost 1,900 square miles of coastal wetlands, greatly reducing the buffer zone between the city and the sea.

"That means the rising sea is coming closer and closer and closer to this one million person metropolis and this two million person region that is relying more and more on these levees and flood walls to keep out that water," says Campanella. "So by the early 21st century we have set the stage for a catastrophe." The fact that half the city was below the level of the sea meant that after Katrina the floodwaters did not disperse as they would elsewhere. Instead they lingered for weeks in the bowl formed by the city.

The experience of New Orleans shows that existential urban decay, the real death of cities, is rarely the result of a single catastrophe. "Suddenly there's nothing there and the city falls apart," says Jennifer Cole of RUSI. "They're not caused by terrorist attacks, they're caused by generally slow, economic decline that suddenly reaches a tipping point. It's not a shock driven model."

That statement hints at a fundamental truth. Planning for catastrophe is a crucial exercise for city fathers, but it needs to take place as part of a wider assessment of real risk. Come hell, high water or terrorist outrage, London will probably be OK. The danger of planning for shock is that it can conceal a failure to deal with real dangers that are slower and less dramatic.

In the case of London, the enthusiastic prostitution of the British capital to the international super rich has pushed the cost of living up far beyond inflation. Between January and May of 2014 the average price of a London home rose by almost £80,000, according to data from the estate agency Rightmove – £80,000 is around three times the median UK household wage.

At the close of Daniel Percival's 2004 film Dirty War a mélange of news reports indicate that three-and-a-half square miles of central and eastern London may have to remain sealed off for as long as 30 years due to lingering radiation.

"Thousands of businesses caught in the contamination zone have been forced to close, millions of pensions, savings and trust funds may never recover," an announcer says. The real dénouement follows: "As London house prices continue to plummet, analysts warn that the full cost of the bombing is impossible to calculate."

The fact that it would take a beeping Geiger counter to make its housing affordable shows better than any fire drill where London's real vulnerabilities lie.

Correction: Comments by Jennifer Cole were amended to add context and clarity and properly distinguish between a 'dirty bomb' and a lower-level radiological dispersion device.