'I was drenched in sweat,' he says. 'People were shouting, the siren was blaring. But a feeling inside told me something was wrong.'

It was. Weeks later, a malfunction was discovered in one of the satellites. Colonel Petrov had averted a nuclear holocaust.

More than 20 years on, this potential celebrity is all but forgotten, ignored by the Russian public. A commission of senior officers interrogated him in the wake of the scare and he was disciplined on a technicality: failing to make contemporaneous notes of the incident in a logbook. Not long after, he left the military.

Colonel Petrov's decisive act remained a secret until the mid-1990s when Russian journalists tracked him down and a smattering of articles appeared about the incident. He then slipped out of view once more.

Now, like a great many elderly Russians, he wavers on the brink of poverty, unrecognised and unrewarded.

The memory of that fateful night still burns bright. It was midnight on September 26 when Colonel Petrov went on duty at the Serpukhov-15 early warning centre south of Moscow.

Perched on a mezzanine overlooking the main hall, where small groups of workers sat at clusters of computer terminals, he cast his eye over a familiar scene.

Immediately to his front was a bank of monitors, and beyond them, stretching two storeys high, a map of the world with the US and the Soviet Union picked out in green lights.

As Colonel Petrov settled into his chair, thousands of kilometres away in Northern Ireland, 38 IRA prisoners had just broken out from Belfast's Maze prison. In the US, cinemagoers were flocking to Sunday afternoon matinees of Flashdance and Return of the Jedi.

Colonel Petrov's thoughts were closer to home as he worked his way through a series of routine checks. The mood in the command centre was sombre. Three weeks earlier, tensions between the US and the Soviet Union had soared when the Soviet military shot down a Korean Air Lines jet that strayed over Soviet airspace, killing all 269 people on board. Then, suddenly, came the moment that every commander dreaded. A siren began to wail and a red button flashed with one word: 'Start'.

'The first signal said one rocket had been launched,' says Colonel Petrov, sitting in the shabby apartment he shares with his son in Fryazino, near Moscow. 'In a few moments, it was recording a full-scale attack of five missiles.'

Immediately, a series of computer verifications swung into motion. All confirmed the attack was genuine. The workers below Colonel Petrov stood up from their seats as lights winked on a single location on the map of the US. 'I had to shout at them to keep silent,' the colonel says.

It would take a Minuteman intercontinental ballistic missile less than half an hour to cross the Atlantic. Now, a message had to be passed to warning-system headquarters and from there to the Soviet leader Yuri Andropov in time for him to give orders for a retaliatory strike on the US. Colonel Petrov had nine minutes to assess the threat.

With a telephone to his superiors in one hand and an intercom to give orders to his 240 subordinates at the command centre in the other, the lieutenant-colonel passed an agonising three minutes.

'If I had only used my brain, I would have had to report that the strike was real,' he says. 'But my intuition told me it was not. And, I thought, if the US is going to launch a nuclear war, it does not do it from a single position with five missiles. I reported the attack was false.'

By this decision, all thoughts of retaliation were nipped in the bud. But there were still more painful minutes of waiting until it was clear that no missiles were raining down. When realisation finally dawned that a nuclear nightmare had been averted, Colonel Petrov's colleagues congratulated him enthusiastically. A special commission set up to investigate the incident over the following weeks was less admiring; many hours of interrogation followed and nobody thanked him.

The inquiry concluded that the satellites tracking missile launches had been fooled into reading missile launches by the sun's reflection bouncing off the tops of clouds. 'If they had rewarded me, then it would have been necessary to admit that the technology was faulty - and nobody wanted to do that,' says Colonel Petrov, who says, nonetheless, that he is not bitter about the way he was treated.

'I was just doing my job, that's all I've ever said,' he says.

Two decades after the incident, experts are convinced of the significance of his judgment that night. According to Bruce Blair, director of the US Centre for Defence Information, 'this is the closest we've come to accidental nuclear war'.

Perhaps more significant, many analysts say there is potential for other dangerous false alarms as Soviet equipment still in use deteriorates over time.

'As much as 30 per cent of the Russian horizon is now lacking satellite coverage of missile launches,' says Jon Wolfsthal, a nuclear-weapons expert at the Carnegie Endowment for International Peace in Washington.

'There is a glaring vulnerability to a false signal or a set of circumstances that could lead a Russian president to believe a US missile attack is underway. That should make us very worried indeed.'