1970-1979 | Nuclear Armageddon

Ministers and MPs learn of Harold Wilson’s secret H-bomb test

Harold Wilson (LBJ Library via Wikimedia) and a nuclear test blast (US Department of Energy via Wikimedia.)
Harold Wilson (LBJ Library via Wikimedia) and a nuclear test blast (US Department of Energy via Wikimedia.)

24 June 1974

On 24 June 1974, Prime Minister Harold Wilson made a statement in the House on Britain’s nuclear deterrent. The previous year, the Labour Party Conference had voted by a clear majority to close down all nuclear bases in the United Kingdom and many Labour MPs had taken their seats ready to denounce any proposal for a new test.   They were flabbergasted when Wilson explained, to cheers from a number of Tory MPs, that Britain had already secretly tested a nuclear device, several weeks earlier, in America’s Nevada desert.1

Wilson explained that the vote at the party’s annual conference had not received the necessary two thirds majority to be accepted as official policy. However, he found it much more difficult to justify the need for secrecy.  Even the Foreign Secretary, James Callaghan, claimed that he had had no prior knowledge of the test, explaining privately to colleagues that ‘it’s the PM’s sphere and he plays these matters close to his chest.’At a Cabinet meeting two days later, Wilson informed ministers that he ‘could not consult’ them because ‘a leak of any kind would have very serious effects for reasons I can’t give now.’  Some ministers were not convinced by such a convenient pretext, including Barbara Castle who pointed out that ‘the French didn’t seem to need all this secrecy: they just calmly announced their tests were taking place.’ She commented in her diary that it was ‘appalling that these things can be done without the knowledge of Cabinet.’3

The Daily Mirror expressed its amazement at the prime minister’s deliberate attempts to keep the public in the dark.  In an editorial on 25 June, it noted that ‘the newspapers which forecast that an underground test in Nevada was on its way were out of date. It had already happened.’ It wondered whether Wilson would even have said anything ‘if his hand had not been forced by press reports ? Or should we all have been kept in ignorance ?’ It added that ‘in a free society, with open government, decisions should be announced and defended while it is still possible to defend them. Not when it is too late.’4


  1. Anger over the Secret H-Bomb,’ The Daily Mirror, 25 June 1974, p. 1.
  2. Barbara Castle, The Castle Diaries, 1964-1976, Papermac, London, 1990, p. 470.
  3. Ibid., p. 471.
  4. ‘Mr Wilson’s Secret Bomb,’ The Daily Mirror, 25 June 1974, p. 2.

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