London is a major terrorist target , having been subjected to repeated Provisional Irish Republican Army ( IRA ) bombings during the Troubles and more recently 7 July 2005 London bombings by Muslim extremists . In the late 1980s the IRA planned a campaign to disrupt the City of London . Two massive truck bombs were exploded in the City of London : the Baltic Exchange bomb on 10 April 1992 , and just over a year later the Bishopsgate bombing . The Corporation of the City of London responded by altering the layout of access roads to the city and putting in checkpoints to be manned when the threat level warrants it ; these measures are known as the " ring of steel " a name taken from the more formidable defences that , at that time , ringed the centre of Belfast
7 July 2005 London bombings
7 July 2005 London bombings
Fortifications of London