Here's what would happen if a nuclear strike was launched on Portsmouth

Russia claimed to have fired warning shots toward HMS Defender, which is currently on deployment in the Black Sea.

However the Ministry of Defence denied these claims.

Onboard BBC defence correspondent Jonathan Beale recorded the moment a Russian commander warned the British ship: ‘if you don’t change course, I will be fire’.

The Russian warning continued: ‘If you cross the border line, I will fire.’

The warning caused crew to put on protective masks and clothing in preparation for firing shortly before a volley of fire could be heard out of range.

Portsmouth-based HMS Defender was travelling through an internationally recognised shipping lane off the coast of Crimea.

But what if tensions were to escalate higher?

During the Cold War, in particular in the 1970s and 1980s when relationships were most strained between the West and the Soviet Union, at least 38 towns and cities in Britain were feared to be at risk from a nuclear strike launched by the USSR.

Dozens of army, navy and air force bases were also earmarked for destruction, with Portsmouth Naval Base topping the list of strategic targets.

The city is home to the majority of the Royal Navy’s fleet, as well as the Senior Service’s HQ where much of its top brass are located.

Bases in nearby Gosport and Fareham also house thousands sailors.

What would theoretically happen if a nuclear strike was launched on Portsmouth?

An interactive tool called outrider.org shows what damage would be caused by the bomb.

It allows people to enter specific cities and choose between four types of bombs – including the USSR’s 50,000 KT Tsar Bomba.

The map simulates the bomb dropping on the area and shows the extent of fireball, shock wave, radiation, and heat.

It also tells users the number of fatalities and injuries that would occur as a result.

If the Tsar Bomba, the largest USSR bomb detonated, was dropped on Portsmouth it is estimated there would be 561,678 fatalities and 464,047 injuries.

The heat from the bomb would travel north as far as Basingstoke, and south, past the bottom of the Isle of Wight, and the shockwave from the blast would be 345.04 square miles.

Radiation would be spread over 30 square miles. Outrider says: ‘These particles damage the human body at a cellular level. Absorbing too many in a short period results in acute radiation poisoning.’

What can be done about nuclear weapons?

Outrider also offers advice about what you can do about nukes.

It includes talking to your elected officials, vote for candidates who are opposed to nuclear weapons and the threat they pose to humanity and donate money to organisations that work towards nuclear arms reduction – such as Global Zero and Bulletin of the Atomic Scientists.

A message from the Editor, Mark Waldron

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