The Downing Street mortar attack was carried out by the Provisional Irish Republican Army (IRA) on February 7, 1991. The IRA launches three homemade mortar shells at 10 Downing Street, London, the headquarters of the British government in an attempt to assassinate prime minister John Major and his war Cabinet, who were meeting to discuss the Gulf War.

During the Troubles, as part of its armed campaign against British rule in Northern Ireland, the Provisional Irish Republican Army repeatedly uses homemade mortars against targets in Northern Ireland. The IRA carries out many attacks in England, but none involve mortars. In December 1988, items used in mortar construction and technical details regarding the weapon’s trajectory are found during a raid in Battersea, South West London, by members of the Metropolitan Police Anti-Terrorist Branch. In the late 1980s, British Prime Minister Margaret Thatcher is top of the IRA’s list for assassination, following the failed attempt on her life in the Brighton hotel bombing.

Security around Downing Street is stepped up following increased IRA activity in England in 1988. Plans to leave a car bomb on a street near Downing Street and detonate it by remote control as Thatcher’s official car is driving by had been ruled out by the IRA Army Council owing to the likelihood of civilian casualties.

The Army Council instead sanctions a mortar attack on Downing Street and, in mid-1990, two IRA members travel to London to plan the attack. One is knowledgeable about the trajectory of mortars and the other, from the IRA’s Belfast Brigade, is familiar with their manufacture. An active service unit (ASU) purchases a Ford Transit van and rents a garage, and an IRA co-ordinator procures the explosives and materials needed to make the mortars. The IRA unit begins making the mortars and cutting a hole in the roof of the van for the mortars to be fired through. Once preparations are complete, the two IRA members return to Ireland, as the IRA leadership considers them valuable personnel and does not wish to risk them being arrested in any follow-up operation by the security services. In November 1990, Thatcher unexpectedly resigns from office, but the Army Council decides the planned attack should still go ahead, targeting her successor, John Major. The IRA plans to attack when Major and his ministers are likely to be meeting at Downing Street and wait until the date of a planned cabinet meeting is publicly known.

On the morning of February 7, 1991, the War Cabinet and senior government and military officials are meeting at Downing Street to discuss the ongoing Gulf War. As well as the Prime Minister, John Major, those present include 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 begins, an IRA member is driving the van to the launch site at the junction of Horse Guards Avenue and Whitehall, about 200 yards from Downing Street.

On arrival, the driver parks the van and leaves the scene on a waiting motorcycle. Several minutes later, at 10:08 AM, as a policeman is walking towards the van to investigate it, three mortar shells are launched from a Mark 10 homemade mortar, followed by the explosion of a pre-set incendiary device. This device is designed to destroy any forensic evidence and set the van on fire. Each shell is four and a half feet long, weighs 140 pounds, and carries a 40-pound payload of the plastic explosive Semtex. Two shells land on Mountbatten Green, a grassed area near the Foreign and Commonwealth Office. One explodes and the other fails to detonate. The third shell explodes in the back garden of 10 Downing Street, 30 yards from the office where the cabinet is meeting. Had the shell struck 10 Downing Street itself, it is likely the entire cabinet would have been killed. On hearing the explosion, the cabinet ducks under the table for cover. Bomb-proof netting on the windows of the cabinet office muffle the force of the explosion, which scorches the back wall of the building, smashes windows and makes a crater several feet deep in the garden.

Once the sound of the explosion and aftershock has died down, the room is evacuated, and the meeting reconvenes less than ten minutes later in the Cabinet Office Briefing Rooms (COBR). No members of the cabinet are hurt, but four people receive minor injuries, including two police officers injured by flying debris. Immediately after the attack, hundreds of police officers seal off the government district, from the Houses of Parliament to Trafalgar Square. Until 6:00 PM, civilians are kept out of the area as forensic experts combed the streets and government employees are locked in behind security gates.

The IRA claims responsibility for the attack with a statement issued in Dublin, saying, “Let the British government understand that, while nationalist people in the six counties [Northern Ireland] are forced to live under British rule, then the British Cabinet will be forced to meet in bunkers.” John Major tells the House of Commons that “Our determination to beat terrorism cannot be beaten by terrorism. The IRA’s record is one of failure in every respect, and that failure was demonstrated yet again today. It’s about time they learned that democracies cannot be intimidated by terrorism, and we treat them with contempt.” Leader of the Opposition Neil Kinnock also condemns the attack, stating, “The attack in Whitehall today was both vicious and futile.” The head of the Metropolitan Police Anti-Terrorist Branch, Commander George Churchill-Coleman, describes the attack as “daring, well planned, but badly executed.”

A further statement from the IRA appears in An Phoblacht, with a spokesperson stating “Like any colonialists, the members of the British establishment do not want the result of their occupation landing at their front or back doorstep … Are the members of the British cabinet prepared to give their lives to hold on to a colony? They should understand the cost will be great while Britain remains in Ireland.” The attack is celebrated in Irish rebel culture when the band The Irish Brigade releases a song titled “Downing Street,” to the tune of “On the Street Where You Live,” which includes the lyrics “while you hold Ireland, it’s not safe down the street where you live.”