`There are people who don't want the election to take place. They want a state of emergency. There will be a bomb on the metro." A person with links to the security agencies that replaced the KGB told me that on the afternoon of June 11th, 1996.

That evening a bomb exploded in a metro carriage between Tulskaya and Nagatinskaya stations in south central Moscow. Four people were killed instantly, others were seriously injured. The rest of the passengers made their way to safety along a dark metro tunnel that rapidly filled with smoke from a fire in the bombed carriage.

Some days later, as the presidential poll advanced, my informant spoke to me again. "You should pay attention," he said, to President Yeltsin's health. There are people who can make him ill." Next day Mr Yeltsin went missing. Appointments were cancelled. He failed to appear on TV in the last days of the campaign.

It transpired that not even the best informed people knew what had happened. By chance, I met the American ambassador, now Assistant Secretary of State Thomas Pickering, in the course of a Sunday morning stroll in the grounds of the Novodevichy Monastery. Mr Yeltsin's whereabouts were a mystery, he said. "We know as much as you," he told me and I was tempted to tell him that perhaps I knew more than he did. Instead, I let the matter pass.

It was revealed later that Mr Yeltsin had suffered a major heart attack shortly after my informant told me to pay attention to the president's health. Attempts to reach the informant again have consistently failed. I was told recently he had left the country.

Although the links between my informant's "tip-offs" and the events that followed may have been coincidence, I began to treat Moscow's myriad conspiracy theories with more respect than usual.

The motives for the bomb that killed eight and maimed dozens in Moscow on Tuesday may be as simple as those suggested by the city's mayor, Mr Yuri Luzhkov, who described the bombing as "100 per cent Chechen". On the other hand, they may not.

Interestingly, Mr Luzhkov took a totally different line after the 1996 metro bomb. Asked about possible Chechen involvement he ruled it out, saying: "It was an act against me and against President Yeltsin."

If Mr Luzhkov lost face after that incident, there was worse to come. Last September, two bombs in distant workingclass suburbs of Moscow killed more than 200 people in a week. At the site of one of the explosions people blamed Mr Luzhkov for not ensuring their safety. One woman disagreed and told me: "It's Yeltsin's fault." Another woman immediately challenged her: "Yeltsin's not a person, he's a mummy. It's the mayor who should protect us."

Those two bombs were expertly placed in order to cause as many casualties as possible. The first, at Pechatniki in the south-east of the city, caused the central section of a vast apartment block to collapse. The bombers exploited flaws in the architectural design. In the second, at Kashirskoye Chaussee, the building was older and sturdier. The bombs were placed in such a way that the entire building imploded. Panes of glass in nearby apartment blocks remained intact. An image of Lenin on a flimsy panel of mosaic gazed unscarred at the devastation.

Vladimir Putin, then Prime Minister, immediately blamed the Chechen separatists. Russians, who had been strongly against the first Chechen war in which more than 30,000 unarmed civilians were killed, began to support military action. Soon afterwards what had been a limited campaign against militants in the neighbouring territory of Dagestan became a full-scale war in Chechnya. Victory and the capture of Grozny were repeatedly declared. The successful pursuit of the war was considered to be a major factor in Mr Putin's success in the presidential elections.

Declarations of victory have now been revised. The war continues and TV reports daily casualties of a dozen soldiers here and a dozen there. Earlier this year more than 100 soldiers from the north-western city of Pskov were killed in action in the space of two weeks. There are signs that public opinion may be turning against the war.

The most important separatist leader, Mr Aslan Maskhadov, has denied Chechen involvement in this week's bombing. There are, however, many separatist units not under Mr Maskhadov's control and the bombing of the underpass at Pushkin Square could be to their benefit.

The place was obviously chosen to inflict the highest number of casualties. The underpass has links to three of the city's busiest metro stations which between them serve 120,000 passengers daily. It is lined with shops and kiosks. At its north-western corner it is the main crossing point for customers at Moscow's largest McDonald's. To the north-east it links with offices of the important newspaper Izvestiya. At the south-west corner is the elegant Galerea Aktyor, a shopping arcade with prestige outlets such as jewellers Tiffany's of New York. Across the street on the south-west corner of the square is a large delicatessen specialising in Armenian food and drink.

It can be seen from this that large numbers of commuters, wealthy new Russians, young McDonald's clients, newspaper workers and members of an ethnic minority community regularly use the underpass. For someone intending to instil terror into the largest possible cross-section of Moscow residents this was the ideal place to plant a bomb.

Most Russians instinctively blame Chechens for the blast and they may be right. It has brought the war to the forefront of people's consciousness once more.