On this day - 15 May

During World War 2 the UK and US had collaborated on weapons research and construction, with many of the top UK scientists working on the Manhattan Project. After the end of the war, the UK were concerned that this had put the US ahead technologically when it came to development of nuclear weapons and wanted to advance their knowledge. This led to Operation Grapple; a series of nine nuclear explosions set off by the UK while testing hydrogen and atomic bombs. This led to confirmation the UK were recognised as the third owner of thermonuclear weaponry worldwide.

On May 15th 1957, the Grapple 1 mission was undertaken. A bomb was dropped from a bomber aircraft and had been designed to detonate at a certain altitude above the ground in order to reduce and nuclear fallout. The test was carried out near to Malden Island which is part of a coral atoll in the Pacific Ocean. The test was successful but the bomb did not reach the level of capability it was designed to reach, leading to design modifications being made before further tests.