(Reuters) - Police said on Monday they had been warned of a bomb in central London, a day before the Queen makes a historic visit to Ireland.
Here is a timeline of some of the worst bomb attacks on mainland Britain by Irish dissident groups in the last 35 years.
February 1974 - Coach carrying soldiers and families in northern England is bombed by the Irish Republican Army (IRA). Twelve people killed, 14 hurt.
October-November 1974 - Wave of IRA bombs in British pubs kills 28 people and wounds more than 200.
July 1982 - Two IRA bomb attacks on soldiers in London’s royal parks kill 11 people and wound 50.
December 1983 - IRA bomb at Harrods department store kills six.
October 1984 - Prime Minister Margaret Thatcher’s cabinet narrowly escapes IRA bomb that kills five people at Brighton hotel during Conservative Party’s annual conference.
September 1989 - Bomb at Royal Marines Music School in Deal, southeast England, kills 11 and wounds 22.
February 1990 - Explosion at Army recruitment centre in Leicester. Two wounded.
May 1990 - Seven wounded by blast at Army Educational Service headquarters in London suburb of Eltham.
May 1990 - One soldier is killed and another wounded by car bomb in Wembley.
June 1990 - Soldier is shot dead at train station in Lichfield.
February 1991 - IRA comes close to killing Prime Minister John Major and key cabinet members in a mortar attack on Downing Street. One of three mortar bombs slammed into garden behind building, exploding within 50 feet (15 metres) of the target.
April 1992 - Huge car bomb outside Baltic Exchange in London’s financial district kills three people and wounds 91.
March 1993 - Bombs in two litter bins in Warrington kill two boys aged three and 12.
April 1993 - IRA truck bomb devastates Bishopsgate area of London’s financial district, killing one and wounding 44.
February 1996 - Two people die when IRA paramilitaries detonate large bomb in London’s Docklands area.
March 2001 - Car bomb explodes outside BBC’s London headquarters. Police say the Real IRA, a republican splinter group opposed to the IRA’s cease-fire, was behind the blast. One man was wounded.
May 2011 - A warning comes from Irish dissident republicans opposed to the peace process in Northern Ireland.
Writing by David Cutler; London Editorial Reference Unit