March 2001: A car bomb explodes outside the BBC's London headquarters. Police say the Real IRA, a republican splinter group opposed to the IRA's ceasefire, was behind the blast. One man was wounded.

Dec. 22, 2001: Briton Richard Reid, the would-be shoe-bomber who failed to blow up an American Airlines flight from Paris to Miami, is arrested.

Sept. 11, 2002: Some 1,000 British Muslims gather at the Finsbury Park mosque to "celebrate" the bombing of the World Trade Center. The Metropolitan Police deploy a force 500 strong to protect the meeting, chaired by Egyptian-born engineer Abu Hamza.

Jan. 8, 2003: Police discover equipment for making ricin in a north London apartment and arrest six men of North African origin. Ricin, derived from the castor bean plant, can trigger severe diarrhea, shock and death. Traces of ricin were found by U.S. troops at suspected al Qaeda sites in Afghanistan.

Jan. 14, 2003: British policeman Stephen Oake is killed during a raid on an apartment in Manchester, where three North African men are arrested as part of an investigation into the ricin plot. The men are later charged by a London court with conspiring to produce a chemical weapon.

July 7, 2005: Four British-born Muslim men blow themselves up, killing 56 including themselves, and injuring about 700, on three London Tube trains and a red double-decker bus, in the first suicide-bomb attack on a major Western city.

July 21, 2005: Just two weeks after the horrible attacks on London's transport, British police say four men attempted to carry out a second wave of attacks on three London underground stations and one bus.

August 2006: A plot to blow up planes in flight from the UK to the US and commit "mass murder on an unimaginable scale" was disrupted.

June 29, 2007: Police defuse a bomb in an abandoned car in the Haymarket, a busy street in the tourist heart of central London.

Sources: Reuters, June 29, 2007, Worst bomb attacks on mainland Britain and Wall Street Journal June 29, 2007 // U.K. Terror Chronology]