Operation Crossroads
There were only seven nuclear bombs in existence in July 1946. The two bombs used in the test were Fat Man plutonium implosion-type nuclear weapons of the kind dropped on Nagasaki. The "Able" bomb was stenciled with the name "Gilda" and decorated with an "Esquire" magazine photograph of Rita Hayworth, star of the 1946 movie, "Gilda". The "Baker" bomb was "Helen of Bikini." This femme-fatale theme for nuclear weapons, combining seduction and destruction, is epitomized by the use in all languages, starting in 1946, of "bikini" as the name for a woman's two-piece bathing suit.
William Penney, Baron Penney
Along with RAF Group Captain Leonard Cheshire, he accompanied the American Team to Tinian Island from which the Hiroshima and Nagasaki missions were flown. On 9 August 1945 he witnessed the bombing of Nagasaki. The US authorities had controversially stopped them seeing the Hiroshima detonation, but at the last minute Penney and Cheshire were granted permission to fly in the B-29 "Big Stink", one of the observation planes that accompanied the Nagasaki weapon delivery bomber "Bockscar". Due to the belated permission, "Big Stink" missed its rendezvous with the bomber at Nagasaki. They saw the Nagasaki detonation from the air at a distance. As the leading expert on the effects of nuclear weapons, Penney was a member of the team of scientists and military analysts who entered Hiroshima and Nagasaki following the Japanese surrender on 15 August 1945 to assess the effects of nuclear weapons.