The Queen's cousin Lord Louis Mountbatten, a highly-decorated former Royal Navy officer, Chief of the Defence Staff and Viceroy of India, was assassinated by an IRA bomb on this day in 1979

As reported in the video above, Mountbatten's fishing boat Shadow V was “blown to smithereens” off the coast of Mullaghmore, a small village in Sligo, around 12 miles from the border with Northern Ireland. One of the Earl's twin grandsons, Nicholas Knatchbull, 14, and Paul Maxwell, 15, a local boy, also died in the explosion.

All seven occupants of the boat were thrown into the water by the blast at around 11.45am. Fishermen raced to rescue, but the Earl died of his injuries shortly after being pulled out of the water. Another passenger, the Dowager Lady Brabourne, 83, would die the following day.

A police officer sorts through wreckage of the boat, Shadow V.

Nicholas’ identical twin Timothy, the Earl’s eldest daughter Patricia, Lady Brabourne and her husband Lord John Brabourne, would survive the explosion despite suffering serious injuries.

[Read more: July 20, 1982: Eleven soldiers killed as twin IRA bombs rock London's Royal Parks]

The IRA issued a statement taking responsibility for what they called the Earl’s ‘execution’. Several weeks later, Sinn Fein vice-president Gerry Adams would add: “What the IRA did to him is what Mountbatten had been doing all his life to other people; and with his war record I don't think he could have objected to dying in what was clearly a war situation.”

Earl Mountbatten, photographed in 1959.

Lord Mountbatten had spent summers at his Irish home, the nearby Classiebawn Castle, for many years and was a well-known figure around Mullaghmore, where his unguarded boat was moored. The Earl had never had a bodyguard.

He would receive a full ceremonial funeral at Westminster Abbey on September 5 in the presence of the Queen and members of the Royal family, his coffin having been drawn in procession by 118 naval ratings. The Earl was later buried at Romsey Abbey.