restaurant in 2005, the attack on which preceded the siege
In 1974 and 1975, London was subjected to a 14-month campaign of gun and bomb attacks by the Provisional IRA. Some 40 bombs exploded in London, killing 35 people and injuring many more. In one incident the Guinness Book of Records co-founder and conservative political activist Ross McWhirter was assassinated; he had offered a £50,000 reward to anyone willing to inform the security forces of IRA activity.
The four members of what became known as the "Balcombe Street gang", Martin O'Connell, Edward Butler, Harry Duggan and Hugh Doherty, were part of a six-man IRA Active Service Unit (ASU) that also included Brendan Dowd and Liam Quinn. Quinn had recently shot dead police constable Stephen Tibble in London after fleeing from police officers. The flat he was seen fleeing from was discovered to be a bomb factory used by the unit.
The Balcombe Street siege started after a chase through London, as the MPS pursued Doherty, O'Connell, Butler and Duggan through the streets after they had fired gunshots through the window of Scott's restaurant in Mount Street, Mayfair. They had thrown a bomb through the restaurant window a few weeks before on 12 November 1975, killing one person and injuring 15 others. The MPS Bomb Squad had detected a pattern of behaviour in the ASU, determining that they had a habit of attacking again some of the sites they had previously attacked. In a scheme devised by a young detective sergeant, the MPS flooded the streets of London with plain-clothes officers on the lookout for the ASU. The four IRA men were spotted as they slowed to a halt outside Scotts and fired from their stolen car.
Inspector John Purnell and Sergeant Phil McVeigh, on duty as part of the dragnet operation, picked up the radio call from the team in Mount Street as the stolen Ford Cortina approached their position. With no means of transport readily available, the two unarmed officers flagged down a taxi cab and tailed the men for several miles through London, until the IRA men abandoned their vehicle. Purnell and McVeigh, unarmed, continued the pursuit on foot despite handgun fire from the gang. Other officers joined the chase, with the four IRA men running into a block of council flats in Balcombe Street, adjacent to Marylebone station, triggering the six-day stand-off. Purnell was subsequently awarded the George Medal for his bravery. Several other police officers were also decorated.