The six-day Balcombe Street siege begins on December 6, 1975, when four Provisional Irish Republican Army (IRA) gunmen take a couple hostage in Balcombe Street, London.

In 1974 and 1975, London is subjected to a 14-month campaign of gun and bomb attacks by the Provisional IRA. Some 40 bombs explode in London, killing 35 people and injuring many more. The four members of what becomes known as the “Balcombe Street gang,” Joe O’Connell, Edward Butler, Harry Duggan and Hugh Doherty, are part of a six-man IRA Active Service Unit (ASU) that also includes Brendan Dowd and Liam Quinn.

The Balcombe Street siege starts after a chase through London, as the Metropolitan Police pursues 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. The four IRA men ultimately run into a block of council flats in Balcombe Street, adjacent to Marylebone station, triggering the six-day standoff.

The four men go to 22b Balcombe Street in Marylebone, taking its two residents, middle-aged married couple John and Sheila Matthews, hostage in their front room. The men declare that they are members of the IRA and demand a plane to fly both them and their hostages to Ireland. Scotland Yard refuses, creating a six-day standoff between the men and the police. Peter Imbert, later Commissioner of the Metropolitan Police Service, is the chief police negotiator.

The siege ends peacefully on December 12, 1975, after the men free their two hostages and surrender following several days of intense negotiations between Metropolitan Police Bomb squad officers, Detective Superintendent Peter Imbert and Detective Chief Superintendent Jim Nevill, and the unit’s leader Joe O’Connell, who goes by the name of “Tom.” The other members of the gang are named “Mick” and “Paddy,” thereby avoiding revealing to the negotiators precisely how many of them are in the living room of the flat. The resolution of the siege is a result of the combined psychological pressure exerted on the gang by Imbert and the deprivation tactics used on the four men. The officers also use carefully crafted misinformation, through the BBC Radio news to further destabilise the gang into surrender. A news broadcast states that the British Special Air Service are going to be sent in to storm the building and release the hostages. This seems to deter the gang and they eventually give themselves up to the police.

The four are found guilty at their Old Bailey trial in 1977 of seven murders, conspiring to cause explosions, and falsely imprisoning John and Sheila Matthews during the siege. O’Connell, Butler and Duggan each receive 12 life sentences, and Doherty receives 11. Each of the men is later given a whole life tariff, the only IRA prisoners to receive this tariff. During the trial they instruct their lawyers to “draw attention to the fact that four totally innocent people were serving massive sentences” for three bombings in Woolwich and Guildford. Despite telling the police that they are responsible, they are never charged with these offences and the Guildford Four and Maguire Seven remain in prison for 15 more years, until it is ruled that their convictions are unsafe.

After serving 23 years in English prisons, the four men are transferred to the high security wing of Portlaoise Prison, County Laois, in early 1998. They are presented by Gerry Adams to the 1998 Sinn Féin Ardfheis as “our Nelson Mandelas,” and are released together with Brendan Dowd and Liam Quinn in 1999 as part of the Good Friday Agreement.