1958 US–UK Mutual Defence Agreement as an atomic spy, caused the proposal to be dropped. The June 1951 defection of Donald Maclean, who had served as a British member of the Combined Policy Committee from January 1947 to August 1948, reinforced the Americans' distrust of British security arrangements. The first British atomic bomb was successfully tested in Operation Hurricane on 3 October 1952, but although it was more advanced than the American bombs of 1946, Britain was still several years behind in nuclear weapons technology. The United States conducted Ivy Mike, the first nuclear test of a true thermonuclear device (also known as a hydrogen
Crack in the World atomic device is used and Rampion's fears prove justified, as the crust of the Earth develops an enormous crack that progresses rapidly. Sorenson discovers that there was a huge reservoir of hydrogen underground, which turned the small conventional atomic explosion into a huge thermonuclear one that was millions of times more powerful. Another atomic device, lowered into the magma chamber of an island volcano, is used in the hope of stopping the crack, but it only reverses the crack's direction. Eventually the crack returns to its starting point at the test site, and a huge chunk of the planet outlined