The Balcombe Street gang, made up of IRA members Martin O'Connell, Edward Butler, Harry Duggan and Hugh Doherty, carried out a bombing campaign in London in 1974 and 1975. They were arrested after a six day standoff at Balcombe Street.
The art gallery at Buckingham palace was considered as a target.The four had also targeted some of London’s most famous locales as possible targets, including the Royal Courts of Justice, London Stock Exchange, Imperial War Museum and the British Museum.
Files also show that the gang targeted high level military personnel, police officers and legislators. Though the names of these individuals have not been released, authorities have said that the list of names was not a "death list.”
The files were amassed from evidence collected from the apartment the gang worked out of in North London.
The four members of the Balcombe Street gang were all sentenced to life in prison in 1977, but were released under the terms of the Good Friday Agreement in 1999.