The 1991 Mortar Attack On Downing Street
- Daniel Holland
- Feb 7, 2023
- 6 min read
At 10.08am on the 7th of February 1991, the centre of British political power was briefly reduced to instinct and survival. Inside Number 10 Downing Street, ministers discussing Britain’s role in the Gulf War suddenly found themselves crouched beneath a Cabinet table as an explosion tore through the garden just yards away. For a few seconds, the boundary between strategic decision making and political violence collapsed.
The attack was not symbolic. It was calculated, rehearsed, and aimed with lethal intent.
On that winter morning, the Provisional Irish Republican Army launched three homemade mortar bombs at the headquarters of the British government in an attempt to assassinate Prime Minister John Major and his war cabinet. One bomb landed in the back garden of Number 10 itself. The others overshot and landed nearby. Had the trajectory shifted by only a few degrees, Britain could have lost an entire Cabinet in a single strike.
Mortars and the logic of distance
During the Troubles, the Provisional IRA increasingly relied on homemade mortars as part of its armed campaign against British rule in Northern Ireland. These weapons were not improvised in a casual sense. They were the product of years of trial, error, and adaptation, designed to overcome fortified police stations and military bases.
One of the most notorious examples was the Newry mortar attack of 28th February 1985, when nine members of the Royal Ulster Constabulary were killed by a single mortar round fired into a police station yard. That attack demonstrated the strategic appeal of mortars. They allowed the IRA to strike from distance, bypass physical barriers, and reduce the risk to attackers.
While the IRA carried out numerous bombings and shootings in England throughout the 1970s and 1980s, it had never used mortars on the British mainland. That changed with a discovery in December 1988, when officers from the Metropolitan Police Anti Terrorist Branch raided premises in Battersea, South London. Inside, they found materials used in mortar construction alongside technical calculations relating to firing angles and trajectory.
The implication was unsettling. The IRA was thinking beyond Northern Ireland.
Downing Street under pressure
By the late 1980s, Downing Street had already been reshaped by security concerns. Increased IRA activity in England led to a £800,000 programme of defensive upgrades in 1988, including the installation of permanent security gates at either end of the street and a staffed police guard post.
The Prime Minister at the time, Margaret Thatcher, was regarded by the IRA as a priority target following the failed attempt on her life in the Brighton hotel bombing in 1984.
Alternative assassination plans were discussed. One proposal involved detonating a remote controlled car bomb as Thatcher’s official vehicle passed nearby. The IRA Army Council rejected the idea. The likely civilian casualties were considered politically damaging and counter productive.
Instead, the organisation approved a more contained method. A mortar attack.
Planning an unprecedented strike
In mid 1990, two experienced IRA members travelled to London under false identities to plan the operation. One was a specialist in mortar trajectory and ballistics. The other, attached to the Belfast Brigade, had hands on experience manufacturing improvised weapons.
An Active Service Unit purchased a Ford Transit van and rented a garage. An IRA coordinator sourced explosives, piping, detonators, and a pre set incendiary device designed to destroy forensic evidence after launch.
Inside the van, engineers cut a hole through the roof and installed a fixed firing platform capable of launching three mortars simultaneously. The unit conducted reconnaissance around Whitehall, assessing distances, lines of sight, traffic patterns, and escape routes. The aim was to strike the rear of Number 10, where the Cabinet Room overlooked the garden.
Once preparations were complete, the two specialists returned to Ireland. IRA leadership considered them too valuable to risk losing in the aftermath of a London operation.
Then the political landscape shifted.
A change of Prime Minister, not of intent
In November 1990, Margaret Thatcher resigned unexpectedly. Her successor, John Major, inherited both office and risk. The IRA Army Council decided the plan would go ahead regardless. The symbolic value of striking the office of Prime Minister outweighed the change in occupant.
The unit waited until the date of a full Cabinet meeting was publicly known. The presence of senior ministers and military leaders would maximise both impact and lethality.
Inside the Cabinet Room
On the morning of 7th February 1991, John Major’s war cabinet met at Downing Street to discuss the ongoing Gulf War.
Those present included Douglas Hurd, Tom King, Norman Lamont, Peter Lilley, Patrick Mayhew, David Mellor, and John Wakeham. Senior civil servants Robin Butler, Percy Cradock, Gus O’Donnell, and Charles Powell were in attendance, alongside Chief of the Defence Staff David Craig.
As the meeting began, an IRA operative drove the Transit van to the junction of Horse Guards Avenue and Whitehall, approximately 200 yards from Downing Street.
10.08am
Several minutes later, as a police officer approached the unattended van, three mortars fired almost simultaneously from a Mark 10 homemade launcher. Moments later, the incendiary device ignited, engulfing the van in flames and destroying potential forensic evidence.
Each mortar measured four feet six inches in length, weighed approximately 140 pounds, and carried a 40 pound payload of Semtex.
Two shells overshot Downing Street and landed on Mountbatten Green near the Foreign and Commonwealth Office. One detonated. The other failed to explode.
The third shell landed in the back garden of Number 10, exploding roughly 30 yards from the Cabinet Office.
Inside the room, ministers instinctively ducked beneath the table. Bomb resistant netting fitted to the windows absorbed much of the blast force. Brickwork was scorched, windows shattered, and a crater several feet deep was torn into the garden.
Investigators later concluded that a direct hit on the building would almost certainly have killed everyone in the room.
As dust settled, John Major reportedly broke the silence by saying, “I think we had better start again, somewhere else.”
After the blast
The Cabinet Room was evacuated immediately. Less than ten minutes later, the meeting reconvened in the Cabinet Office Briefing Room.
No ministers were injured. Four people suffered minor injuries, including two Metropolitan Police officers struck by flying debris.
Whitehall was sealed off within minutes. Hundreds of police officers established cordons from Trafalgar Square to the Houses of Parliament. Civilians were excluded until 6.00pm as forensic teams examined the blast sites and the remains of the launch vehicle. Government staff already inside the secure zone were locked in for hours.
Claims, statements, and reactions
The IRA claimed responsibility in a statement issued in Dublin:
“Let the British government understand that, while nationalist people in the six counties are forced to live under British rule, then the British Cabinet will be forced to meet in bunkers.”
John Major addressed the House of Commons later that day:
“Our determination to beat terrorism cannot be beaten by terrorism. Democracies cannot be intimidated by terrorism, and we treat it with contempt.”
Opposition leader Neil Kinnock described the attack as “vicious and futile”.
Commander George Churchill Coleman of the Metropolitan Police Anti Terrorist Branch characterised it as “daring, well planned, but badly executed”.
A technician’s verdict
Peter Gurney, head of the Explosives Section who defused the unexploded mortar, offered a rare professional assessment:
“It was a remarkably good aim if you consider that the bomb was fired 250 yards with no direct line of sight. Technically, it was quite brilliant. If the angle of fire had been moved five or ten degrees, those bombs would actually have impacted on Number Ten.”
His words underlined a narrow margin between failure and catastrophe.
Cultural echoes and consequences
A further IRA statement published in An Phoblacht framed the attack as a warning to the British political class. Within republican culture, the operation was later commemorated in song. The band The Irish Brigade released Downing Street, set to On the Street Where You Live, with the line:
“While you hold Ireland, it’s not safe down the street where you live.”
In practical terms, the consequences were immediate. John Major temporarily relocated to Admiralty House while repairs were carried out. Additional guardhouses were installed at both ends of Downing Street, alongside less visible security measures that remain in place today.
The attack permanently altered assumptions about distance, protection, and vulnerability at the heart of British government. It demonstrated that even the most secure locations could be reached with patience, engineering skill, and a willingness to wait.
For a few seconds in February 1991, the British Cabinet came closer to annihilation than at any point since the Second World War. The fact that it did not happen owed less to design than to degrees and chance.
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