At 8.00 a.m. on Friday 3 October 1952, Britain's first atomic bomb was detonated in the hold of a surplus frigate, HMS Plym, moored in the Montebello Islands, 50 miles off the North West Coast of Western Australia. The blast vaporised the Plym, produced a mushroom cloud 2 miles high, and covered the islands and parts of the Australian mainland with fallout.