Lord Louis Mountbatten was the great-uncle of Prince Charles.
The British statesman and naval officer was killed on August 27, 1979, while holidaying at his Irish summer home, Classiebawn Castle in Mullaghmore, County Sligo.
Police had warned Mountbatten of security threats but he went lobster-potting in his 30ft fishing boat, the Shadow V.
A bomb, slipped onto the unmanned boat the night before, was detonated when the boat was about 600 metres from shore.
The boat was destroyed in the blast but 79-year-old Mountbatten, whose legs were almost blown off, was pulled alive from the water. However, he died before rescuers could bring him to shore.
Three others also died in the atrocity; his 14-year-old grandson Nicholas Knatchbull, Paul Maxwell, a 15-year-old crew member, and the Dowager Lady Brabourne, the mother-in-law of Mountbatten's daughter, Lady Brabourne.
Lord and Lady Brabourne, Nicholas Knatchbull's mother and father, survived the blast, along with his twin brother Timothy, but were seriously injured.
The IRA later claimed responsibility for the deaths.
IRA member Thomas McMahon, who was convicted for his part in the bombing, spent 19 years in prison before being freed in 1998 under the Good Friday Agreement.
On the same day of the bombing, the IRA also ambushed and killed 18 British soldiers in what became known as the Warrenpoint ambush.