ABSTRACT
International pressure became more acute in the first half of 1958. AWRE were at that time still thinking in terms of a continuous series of tests single megaton shots once every three or four months. If the UK was to develop improved British nuclear warheads, it had to complete its own tests before any suspension became effective. After Grapple X, the UK was able to design a one-megaton warhead for its Blue Streak missile, but it would be profligate in fissile material and vulnerable to counter measures with no prospect of decreasing the design's vulnerability. The Cabinet Defence Committee invited the Minister of Defence in March 1958 to consider the conditions on which the UK could accept a suspension of nuclear tests unrelated to the cut-off. The US originally wanted the negotiations to begin on 1 October, but because of Grapple Z, the UK suggested 31 October instead and the US agreed.
