Here are some of the worst attacks on mainland Britain in the last 30 years. Most were related to the conflict in Northern Ireland.
February 1974 - Bus 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. Several people are convicted but cleared almost two decades later.
July 1982 - Two IRA bomb attacks on soldiers in London's royal parks kill 11 people and wound 50.
December 1983 - IRA bomb at London's Harrods department store kills six.
October 1984 - Prime Minister Margaret Thatcher's cabinet narrowly escapes IRA bomb that kills five people at hotel in English resort of Brighton during the Conservative Party's annual conference.
September 1989 - Bomb at Royal Marines Music School in Deal, southeast England, kills 11 and wounds 22.
February 1991 - The IRA fires a mortar at Prime Minister John Major's London office. No one is injured.
April 1992 - Huge car bomb outside Baltic Exchange in London's financial district kills three people and injures 91.
March 1993 - Bombs in two litter bins in Warrington, northern England, kill two boys, aged three and 12.
April 1993 - IRA truck bomb hits Bishopsgate area of London's financial district, killing one and injuring 44.
February 1996 - Two people die when IRA members detonate large bomb in London's Docklands area.
March 2001 - A powerful 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 injured.