Underground Testing of Nuclear Warheads Was Kept Secret From Cabinet

Underground testing of British nuclear warheads was kept secret from most cabinet ministers after the US administration was persuaded not to publicize the event, government files reveal.

The labor government's internal debate on updating the United Kingdom's arsenal of Polaris missiles during the mid-1970s involved only the prime minister and three other senior ministers, according to archive documents released today.

Their confidential deliberations were blown wide open, however, by an unusual journalistic scoop - based on a dream - that forced the government to adopt a more transparent policy.

The problem, the prime minister, Harold Wilson, was told in a memo marked "Top Secret" in 1974, was that "we have to improve Polaris if we are going to retain a credible deterrent."

Information from satellite photography indicated that the Russians were developing missile defenses "to which the existing Polaris system would be vulnerable", the memo said.

A meeting was held to discuss the issue involving the prime minister along with his foreign secretary, chancellor and defense secretary.

"There is a long-standing convention," Wilson minuted, "that sensitive questions in the field of foreign affairs, defense matters and on security and intelligence are not necessarily brought before the cabinet for decision."

The Polaris upgrade was first named Super-Antelope, but this was later changed to Chevaline.

Roy Mason, the defense secretary, explained there would have to be new nuclear tests.

"The Super-Antelope program includes one, possibly two, underground nuclear warhead tests," he recorded in March 1974, "the first one being due to be held at the Nevada test site within the next two months."

He recommended Britain proceed with the warhead test "but ask the Americans to delay any announcement".

On May 23 that year, the Ministry of defense informed Downing Street that the test, codenamed Forrester, had been carried out: "There was negligible release of radio activity ... preliminary estimates show that the yield was close to the expected figures."

But official satisfaction at keeping it secret was swiftly punctured. The next month the Daily Express revealed details of the test. The journalist who wrote the story was the veteran defense expert Chapman Pincher.

A Foreign Office official, Crispin Tickell, was asked to investigate. He rang the Express's foreign editor, John Ellison.

Tickell's record of the conversation went as follows: "Mr Ellison said, 'Believe it or not Mr Pincher's source was Mr Pincher himself. He had been on a fishing holiday in Scotland. One morning at breakfast he said he had had a particularly vivid nightmare about a nuclear explosion which he was sure was British.

"'His companions told him that he was obsessed and should go back to fishing. He duly did for three days but on his return to London, he rang up his friends in the Ministry of defense with some such question as: 'What was all that that about a nuclear test?'

"'Eventually he got an answer which was sufficiently equivocal to convince him that he was on the right track. He then wrote his article.'"

Other than forecasting a test which had already taken place, the article was accurate. As Tickell commented: "Against such extra-sensory perception, as well as the best contacts in Whitehall, I feel we are powerless. Mr Pincher remains the greatest."

To avoid further political embarrassment subsequent tests were confirmed by the government within a few hours of taking place.

By 1977 the cost of Chevaline had risen to £810m. Later British nuclear tests were brought to an end by US support for the Comprehensive Test Ban Treaty.