TIMELINE: Militant plots against Britain

(Reuters) - Police in London on Friday defused a car bomb packed with gas, propane and nails that could have killed many people.

Security officials suspect the involvement of al Qaeda-inspired Islamists. Britain, a firm ally of the United States which took part in the invasions of Afghanistan and Iraq, has been a prime target for such groups in recent years.

Following are details of some of the major plots:

March 2004 - Police arrest a group of men suspected of planning attacks using fertilizer-based bombs on various targets including a London nightclub and a big shopping centre; five members of the cell were convicted in April 2007.

August 2004 - Police arrest a group of men led by British al Qaeda operative Dhiren Barot in connection with plans to bomb U.S. financial targets, including the New York Stock Exchange, and stage attacks in Britain. Barot was jailed last November. Seven other men were sentenced earlier this month.

April 2005 - Briton Saajid Badat is jailed for 13 years after admitting to conspiring with "shoe bomber" Richard Reid to blow up aircraft over the Atlantic.

July 7, 2005 - Four British Muslims kill themselves and 52 other people in attacks on London's transport network.

July 21, 2005 - Alleged attempt to set off suicide bombs on three London underground trains and a bus causes huge security alert but no casualties. Six men are currently awaiting the verdict in their trial.

Oct 2005 - Three men arrested in possession of bomb-making manuals including instructions for making a suicide vest. They are now on trial on terrorism-related charges; two of the three are accused of conspiracy to murder.

Aug 2006 - Police say they foiled a plot to blow up airliners flying between Britain and the United States using liquid explosives.

Jan 2007 - Police crack an alleged plot to kidnap and kill a British Muslim soldier. Five men are later charged with terrorism-related offences.