DURING the 1960s military experts said a five-megaton hydrogen bomb dropped on London would produce a crater three-quarters-of-a-mile across and 150ft deep.

At a distance of three miles from the blast, buildings would be totally destroyed by a fireball measuring more than two miles in diameter. Seven miles from the bomb's epicentre and roofs would be ripped off leaving homes gutted.

According to recently declassified Government documents High Wycombe was doomed to face a similar fate if the Russians had launched a nuclear attack on the UK.

A report drawn up by Britain's Joint Intelligence Committee (JIC) in 1967 listed the town as a 'likely' target because of its huge RAF base and Bomber Command bunker at Naphill.

At that time JIC chiefs believed High Wycombe would most probably disappear under two 500-kiloton missiles and a further two one-megaton bombs delivered by air. The strike on the chair-making town would have been part of a wave of 26 attacks calculated to kill 12 million Britons.

These latest glimpses into the horror Cold War scenarios envisaged by the British Government have been revealed by the academic and political historian Peter Hennessy.

In his forthcoming book The Secret State, Mr Hennessy uses recently declassified Whitehall defence documents dating back to the 1960s to paint a disturbing behind-the-scenes picture of the Whitehall corridors of power when the world teetered on the brink of nuclear holocaust.

Mr Hennessy, a professor at the University of London, even enlists the help of a former bomber navigator who gives a disturbing account of how the final order for a nuclear retaliatory strike on Russia would have come from the bomber command bunker deep beneath the Chiltern Hills at Naphill.

It is clear from the information Mr Hennessy has uncovered that High Wycombe's Naphill base, now RAF Strike Command, was a prime target for any foreign aggressor with a nuclear capability but what about now in post-Cold War 2002.

Dale Donovan, information officer at RAF Strike Command High Wycombe in Naphill, said bomber command was disbanded in 1968 when the RAF relinquished its nuclear deterrent in favour of the Royal Navy's Polaris submarines. The subs became the principal carriers of British nuclear weapons in the early 1970s and Bomber Command became Strike Command.

Mr Donovan explained that since the end of the Cold War the RAF has been scaled down and as a result so has the role of the High Wycombe nerve centre.

He added: "As far as the RAF is concerned it [Strike Command] is probably the most important base that they have.

"Having said that there aren't any aircraft here any more but it is an administrative headquarters. It has under its control hundreds of aircraft."

Asked if Strike Command was still a nuclear target, Mr Donovan said: "I honestly don't know."

But throughout the Cold War many people living in Wycombe became worried about a possible nuclear attack.

During the 1980s the High Wycombe Peace Council believed there was a very real threat of a nuclear war erupting. The campaign group even produced a poster showing the town's high street dwarfed by a giant mushroom cloud rising from behind the Guildhall.

Veteran council member 86-year-old Donald Salmon told the Free Press this week that the world situation had completely changed and the group ceased campaigning in the early 1990s.

A spokesman for the Ministry of Defence said Mr Hennessy would have been referring to one-time top secret documents which are now available to the public because they are no longer considered a risk to national security.