This is what will happen if someone fires a nuclear bomb at the UK

The government of Sweden is preparing to distribute a new leaflet to all 4.8 million Swedish households in an effort to increase the nation’s readiness for war, or another major crisis.

Yes, you read that right: Sweden.

“If Sweden is attacked by another country, we will never give up,” they say, alongside tips for avoiding infection and tips for spotting fighter jets and tanks.

It’s a return to Cold War-style domestic planning, and it’s understandable, given the global tensions that abound in the present moment in time, both from Vladimir Putin’s Russia and, of course, from across the Atlantic.

Last year, a war of words between Donald Trump and Kim Jong-un left many concerned that one misstep on either side could be catastrophic.

Trump threatened North Korea with “fire and fury that the world has never seen”, while Kim was thought to be “carefully examining” a strike on the American Pacific territory of Guam.

North Korea has claimed it is capable of reaching the United States with a nuclear weapon - and it’s worth bearing in mind that the distance between Pyongyang and London is shorter than that between Pyongyang and Los Angeles by several hundred kilometres.

The rhetoric was subsequently ramped up, with North Korea carrying out more tests and Trump threatening to destroy North Korea, calling Kim a “rocket man” on a “suicide mission”.

While talks between Trump and Kim Jong-un are scheduled for 12 June and the North Korean leader recently greeted South Korea’s Moon Jae-In in an historic meeting, many experts are warning that progress on denuclearisation from the North Koreans is far from assured.

While it is impossible to know how worried we should be, it’s still worth considering what happens if the unthinkable occurs and a nuclear bomb comes our way. Just for peace of mind, if nothing else.

How long will we have to prepare?

If a nuclear weapon is fired at the UK, multiple sources have suggested it would take a matter of minutes to reach its target. We can anticipate it taking less time to reach the UK from Russia or mainland Europe than from North Korea, due to the distance covered, but ‘about half an hour’ is an appropriate working premise.

This, naturally, does not allow for much creativity in terms of short-term preparation for a blast. Indeed, it may be a challenge for many to even find suitable cover.

According to the United States Department of Homeland Security’s ready.gov website, you are advised to look for immediate shelter, as ‘any protection, however temporary, is better than none at all’. While some protocols will differ from one country to the next, these are just as applicable to the UK as they are to the US.

Should we hide out in old tube stations?

The best potential shelters are those with distance from a blast location, plus thick walls and materials to stand between you and any blast.

Some old and new tube stations fit this description. Hampstead is the deepest tube station at 192 feet below the surface, while Aldwych station – out of use for decades – is one of a number current and former Piccadilly Line stations which have the characteristics required, alongside York Road (near King’s Cross) and Down Street in Mayfair.

Do the old ‘secret bunkers’ still work?

In theory, yes, though civilians would not necessarily have ready access. These are mostly dotted around the English countryside, and it is not known whether any suitable structures remain in London.

The bunkers were never likely to survive a direct hit, but during the Cold War they would have been able to function as de facto safe houses for figures of authority to use as bases.

The watertight bunkers, some of which are still dotted around the UK, were designed to prevent outside forces entering, and would therefore theoretically offer protection against radiation in the aftermath of a blast.

However, these bunkers would now only be usable as fallout shelters (if at all), according to experts, and citizens would be encouraged to take measures to build shelters of their own if given enough warning of a credible nuclear threat.

What would the blast radius be?

If a one megaton nuclear warhead were to hit central London, the Nuke Map website estimates a fireball radius of just under 1km, or an area of just shy of 3km. However the impact goes far beyond that distance.

Within a radius of 7km, most residential buildings are likely to collapse, causing further fatalities. If a nuke were to strike Big Ben, the air blast radius is anticipated to stretch as far north as Arsenal’s Emirates Stadium in Holloway and as far south as Streatham Hill station.

The thermal radiation radius extends even further, however. Encompassing an area of 466km², from Kew Gardens in the west of the capital to City Airport in the east, those affected would be at serious risk of third degree burns and/or permanent scarring.

That’s just for a 1 megaton bomb, remember. The largest ever recorded nuclear weapon ever designed – the USSR’s Tsar Bomba – would carry a fireball radius of 6.1km and a thermal radiation radius stretching as far as Sussex or Bedfordshire.

It would be likely to kill as many as six million people in and around London, and leave a further six million with injuries.

Will there be a mass evacuation?

A 2015 UK government document entitled ‘Nuclear Emergency Planning and Response Guidance’ lays out the theoretical protocol in line with the risk assessments and contingency planning that form a part of the preparations for such an eventuality.

The document points to three potential emergency actions for the population, depending on the level to which they have been affected: in some instances, people will be merely advised to take shelter and lock all doors and windows

The decision whether or not to evacuate will be made by the STAC, and will likely come in situations where ‘the risk to public health posed by an off-site release of radioactive contamination has been identified or is predicted’.

What will the BBC do?

The BBC is officially considered the UK’s ‘emergency broadcaster’ and has its own crisis planning in place.

From the point of view of the authorities, priorities lie with online and local radio coverage from the BBC, rather than television, as well as dispersing relevant information over social media where possible.

In 2008, a pre-recorded message designed to be made public in the case of a nuclear strike (but which was, thankfully, never required) was heard for the first time.

The script, which those at the time were keen to have read by a ‘familiar’ voice, read as follows:

“This is the Wartime Broadcasting Service. This country has been attacked with nuclear weapons.

“Communications have been severely disrupted, and the number of casualties and the extent of the damage are not yet known.

“We shall bring you further information as soon as possible.

“Meanwhile, stay tuned to this wavelength, stay calm and stay in your own homes.

“Remember there is nothing to be gained by trying to get away. By leaving your homes you could be exposing yourself to greater danger.

“If you leave, you may find yourself without food, without water, without accommodation and without protection.

“Radioactive fall-out, which follows a nuclear explosion, is many times more dangerous if you are directly exposed to it in the open.

“Roofs and walls offer substantial protection. The safest place is indoors.

“Make sure gas and other fuel supplies are turned off and that all fires are extinguished. If mains water is available, this can be used for fire-fighting.

“You should also refill all your containers for drinking water after the fires have been put out, because the mains water supply may not be available for very long.

“Water must not be used for flushing lavatories: until you are told that lavatories may be used again, other toilet arrangements must be made. Use your water only for essential drinking and cooking purposes. Water means life. Don’t waste it.

“Make your food stocks last: ration your supply, because it may have to last for 14 days or more. If you have fresh food in the house, use this first to avoid wasting it: food in tins will keep.

“If you live in an area where a fall-out warning has been given, stay in your fall-out room until you are told it is safe to come out. When the immediate danger has passed the sirens will sound a steady note.

“The ‘all clear’ message will also be given on this wavelength. If you leave the fall-out room to go to the lavatory or replenish food or water supplies, do not remain outside the room for a minute longer than is necessary.

“Do not, in any circumstances, go outside the house. Radioactive fall-out can kill. You cannot see it or feel it, but it is there. If you go outside, you will bring danger to your family and you may die.

“Stay in your fall-out room until you are told it is safe to come out or you hear the ‘all clear’ on the sirens.

“We shall be on the air every hour, on the hour. Stay tuned to this wavelength, but switch your radios off now to save your batteries. That is the end of this broadcast.”

However, this will now never be used as the government scrapped the ‘four minute warning’ in 1992.

How about the government?

A ‘Central Government War Headquarters’ was established with a view to being used during the Cold War, but this was ultimately never required.

The HQ is located 120ft underground in Wiltshire, four miles from Chippenham, and occupies an area of 240 acres including a ‘virtual city’, designed to be self-sustaining in the event of an attack.

It remained active into the 21^st century, and might have remained a viable location for government in the event of a fresh nuclear attack, however it is unclear how habitable the location is.

In 2015, it was placed on the Historic England’s At Risk Register, while an unspecified amount of the site is being converted into a storage facility for secure data.

What will the medium and long-term impact be?

A ‘preparedness’ document, part of the same series of government papers, suggests the public health impact of a nuclear strike would likely be twofold. As explained in the document:

‘The first category is possible health effects due to the public being exposed to radioactive materials.

‘The second category is health effects that are not related to radiation exposure but occur instead as the result of stresses (mainly psychological but possibly also physical) that the public experiences.’

Of these two potential impacts, the latter has been most common among previous nuclear crises overseas, though there is no UK-specific example to draw upon.

(Images: Rex Features/Getty)