mortars. The unit began making the mortars and cutting a hole in the roof of the van for the mortars to be fired through. They reconnoitred locations in Whitehall to find a suitable place from which the mortars could be fired at the back of 10 Downing Street, the official residence and office of the British prime minister. Once preparations were complete, the two IRA members returned to Ireland, as the group's leadership considered them valuable personnel and did not wish to risk them being arrested in any follow-up operation by the security services. In November 1990, Thatcher unexpectedly resigned from office, but the Army Council decided the planned attack should still go ahead, targeting her successor John Major. The IRA planned to attack when Major and his ministers were likely to be meeting at Downing Street and waited until the date of a planned cabinet meeting was publicly known. The attack On the morning of 7 February 1991, Major's war cabinet, along with other senior government and military officials, were meeting at Downing Street to discuss the ongoing Gulf War. As well as Major, those present included politicians Douglas Hurd, Tom King, Norman Lamont, Peter Lilley, Patrick Mayhew, David Mellor and John Wakeham; civil servants Robin Butler, Percy Cradock, Gus O'Donnell and Charles Powell; and Chief of the Defence Staff David Craig. As the meeting began, an IRA member was driving the van to the launch site at the junction of Horse Guards Avenue and Whitehall, about from Downing Street. On arrival, the driver parked the van and left the scene on a waiting motorcycle. Several minutes later at 10:08 am, as a policeman was walking towards the van to investigate it, three mortar shells were launched from a Mark 10 homemade mortar, followed by the explosion of a pre-set incendiary device. This device was designed to destroy any forensic evidence and set the van on fire. Each shell was four and a half feet (1.4 m) long, weighed , and carried a payload of the plastic explosive Semtex. Two shells landed on Mountbatten Green, a grassed area near the Foreign and Commonwealth Office. One exploded and the other failed to detonate. The third shell exploded in the back garden of 10 Downing Street, from the Cabinet Office, where the meeting was being held. Had the shell struck 10 Downing Street itself, it is likely the entire cabinet would