It’s hard to imagine anyone who would not be horrified listening to the description of what would happen in a nuclear explosion.

In Countdown to Zero hear what would happen to cities as they are destroyed in the heat of the explosion and horrifying details of how it would wipe out all life, including human, close to the epicentre. Shards of flying glass would also act as harbingers of death to any who were not killed immediately and any remaining doctors would be left helpless, effectively attempting to use put a plaster to staunch a haemorrhage.

The film has been put together by Global Zero an organisation opposed to nuclear weapons and their ability to wipe out millions of lives at the touch of a button.

It’s a sickeningly powerful description of what could happen in this film which is unashamedly putting forward an argument to rid the world of nuclear weapons.

Countdown to Zero is written and directed by Lucy Walker and includes interviews with many former world leaders - the people who had the power to trigger the nuclear button.

Interviewees include former US president Jimmy Carter who recalled the tough decision he might have been compelled to make if a warhead had been heading its way towards him.

“I knew that if the Soviets did launch an attack that it would take 26 minutes for an intercontinental ballistic missile to leave Russian soil and land in Washington or New York. And I had that much time to decide how to respond.”

And ex Russian leader Mikhail Gorbachev described how he and US leader Ronald Reagan had attempted to abolish all their weapons.

Gorbachev recalled at those meetings “we truly opened the door and peeked beyond the horizon”.

Lucy Walker said: “They may not have succeeded - although it did succeed in turning the arms race around - but to me this demonstrates that it took only the political will of two leaders to slice through any amount of bureaucracy, inertia, fear and opposition.”

The documentary also examines to risks of rogue states making their own bomb, terrorists getting hold of sufficient material and know how to build and detonate one, and even estimates the cost of such an operation at around �3 million.

And it looks at the episodes of near misses when we were so nearly on the brink, with preparations under way to fire missiles.

Countdown to Zero, certificate PG, opens on Friday June 24, following screenings on Tuesday June 21, designated Demand Zero Day.