It happened one clear summer morning, August 6, 1945, at 8:15, when three B-29s approached Hiroshima from the north-east.

One of them - Enola Gay - passed over the central part of the city, dropped the bomb, and then took off at full speed.

The bomb exploded 43 seconds later at an altitude of 1 900 feet in a huge fireball, followed by a mushroom cloud of smoke that rose 29 700 feet in the air.