Assassination of Lord Mountbatten

Lord Mountbatten, a retired British statesman and cousin to Queen Elizabeth II, was assassinated on 27 August 1979 off the coast of Mullaghmore, Ireland. Thomas McMahon, an Irish republican and a volunteer for the Provisional Irish Republican Army (IRA), planted a bomb on Mountbatten's boat, the cabin cruiser Shadow V, during Mountbatten's annual summer trip to Classiebawn Castle, his house on the Mullaghmore Peninsula.

The IRA had planned the attack for several months. A bomb team, which included McMahon, constructed a device containing fifty pounds (23 kg) of the explosive gelignite. McMahon placed this on Shadow V on the night of 26 August 1979 before he and his accomplice, Francis McGirl, drove away. They were arrested during a routine stop eighty miles (130 km) from Mullaghmore. McGirl did not have the papers to prove his identity or ownership of the car, and so both men were held by the police.

The bomb was detonated less than two hours later, killing Mountbatten, his grandson Nicholas and Nicholas's grandmother Doreen. Also killed was Paul Maxwell, a boy who was crewing for Mountbatten. Three other passengers were severely injured. When news of the bombing broke, McMahon and McGirl were charged. Five hours after the bomb went off, the IRA ambushed a British Army patrol with two roadside bombs, killing eighteen British soldiers. The attacks were condemned by world leaders and by the media in both the UK and Ireland.

The investigation by the Garda Síochána—the Irish police—found traces of nitroglycerine and ammonium nitrate, two of the ingredients of gelignite, on the clothing of McMahon and McGirl. The tests also found flakes of green and white paint, which matched the paint from Shadow V, on McMahon's boots and jacket, and sand from Mullaghmore in his boots' treads. McMahon was sentenced to life imprisonment in November 1979; McGirl was acquitted.

The bombing led to Margaret Thatcher, the British prime minister, changing the UK's strategy towards Northern Ireland. She introduced an approach in which the intelligence services took a more active role; she appointed Maurice Oldfield as an inter-service intelligence co-ordinator. Donations to NORAID, the US-based organisation that raised funds for the IRA, declined. American intelligence and law enforcement became more proactive in investigating IRA arms procurement in the US, and the Federal Bureau of Investigation set up a specialist unit to combat weapons smuggling to Ireland.