By Dominic Casciani BBC News Online community affairs reporter

The British government in the 1960s was so worried about an American bomber laden with nuclear weapons crashing in the UK it decided the best policy would be to deny everything.

Papers released at the National Archives, formerly the Public Record Office, reveal that Whitehall wanted to block US authorities from ordering evacuations if one of its nuclear weapons fell upon the British countryside.

The debate over how to block the US military from alerting the public - and thereby causing expected national panic - went on for five years as mandarins tried to prepare press statements in the event of a potential catastrophe.

Whitehall feared the publicity surrounding a nuclear accident

But eventually they recognised that US forces would have to alert the public in the worst possible scenario.

The debate began after an accident at RAF Lakenheath in 1956 when an American B-47 bomber crashed on landing and smashed into a bunker holding nuclear weapons.

The following year, the country experienced a civilian nuclear incident when a fire broke out at Windscale power station, later renamed Sellafield.

Against this background, Whitehall asked Washington exactly what the governments would do in the event of an American bomber coming down.

Washington replied it already had a major contingency plan in place to prevent public panic, a strategy which had been tested after a non-nuclear aircraft accident in the US itself.

US discouraged

But London was not having any of it, not least because it feared the press would always ask if nuclear weapons had been involved.

It decided that Washington's freedom to talk to the press should be curtailed.

"It must clearly be for the British government to provide the necessary background should a crash take place of an aircraft carrying a nuclear weapon," concluded one memo.

"The Foreign Office has since asked the Americans to ensure that in the event of such a crash, no press release is issued without prior consultation with the Ministry of Defence.

Any questions about nuclear weapons should be answered on the lines that a further statement will be made by the air ministry as soon as the facts are known Air Ministry document

"It does not seem right that the US authorities should make statements about evacuated areas or about decontamination.

"I think it is certainly right that the Americans should be discouraged from making statements, particularly about evacuation."

By 1960, this policy had hardened to effectively deny everything until it was no long plausible to maintain the line.

In one Air Ministry document, a civil servant describes what to do in various disaster scenarios.

"Initial inquiries from the press should be answered with a factual statement that an aircraft of a named type crashed at a named location at a named time, together with any information about casualties which can be released under normal procedures," said the unnamed official.

The policy reflects deep concern amongst government officials

"If at the time this statement is made a nuclear weapon is known to have been carried or if the position is uncertain, any questions about nuclear weapons should be answered on the lines that a further statement will be made by the air ministry as soon as the facts are known.

"If it is known that no nuclear weapon was involved, the sooner this is stated the better."

Officials suggested there were only two situations where an immediate statement about the presence of a nuclear weapon would be unavoidable: If a bomb was lying within sight of the public, or if one had already exploded.

"If no explosion has occurred it is clearly undesirable to stimulate public interest in the crash by announcing that 'there is no danger of an atomic or high explosive detonation'," he said.

"Until the appearance of such an announcement, the public would not necessarily imagine that any such danger had existed.

"If such an explosion had occurred...it would obviously be necessary as soon as possible to make a statement."

Washington bit its tongue and exercised diplomatic tact.

It agreed to most of the proposed public relations plan.

But it politely suggested that if its personnel were the first on the scene, then they would obviously have the support of the British government to ensure public safety.