What tragedy happened in London in July 2005?
At 08:50, three bombs exploded within fifty seconds of each other on three London Underground trains, a fourth exploding an hour later at 09:47 on a double-decker bus in Tavistock Square. The explosions were caused by home-made organic peroxide-based devices, packed into rucksacks and almost certainly detonated by the bombers themselves. Fifty-six people were killed, including the bombers, and 700 were injured.
