holocaust were triggered by an unusual combination of sunlight and high-altitude cloud formations, wrongly interpreted by the computers as a missile launch.

But although Petrov's conduct under intense pressure initially drew high praise from superiors - there was talk of a medal - an official investigation later accused him of serious disciplinary offences. Petrov was formally reprimanded, demoted and shuffled into a much less responsible post. Convinced he had been made a scapegoat for exposing flaws in the early warning network, he chose to take early retirement and, by some accounts, suffered a nervous breakdown.

It was not until the late-1990s, as President Gorbachev's policy of glasnost (openness) took hold, that the story of that dramatic night in the bunker became public knowledge in Russia. An American expert on Soviet defence doctrines during the Cold War described the incident as "the closest we've come to an accidental nuclear conflict". Contemporary US intelligence reports indicated that the then Soviet leader, Yuri

Andropov, and his top brass were extremely nervous about the possibility that President Ronald Reagan might authorise a devastating first strike against what he had famously dubbed "the evil empire".

By then, Petrov was surviving on a meagre military pension in a squalid apartment block in a town near Moscow, drinking too much and mourning the death of his devoted wife from cancer. He would tell Western journalists that he did not consider himself a hero, just a conscientious officer who did his duty at a moment of great peril for mankind.

Yet within a few years, as word spread of his role in averting what could have become a global catastrophe, he was being feted in the West. In May 2004, the US-based Association of World Citizens awarded him a trophy and $1,000: two years later, health seemingly restored, he was invited to UN headquarters in New York to receive a second award.

Twenty-five years on, a documentary film about Petrov - working title The Man Who Saved The World - is being prepared. It is due for release next summer.