Lord Mountbatten pictured between Princess Anne and the Queen on the balcony of Buckingham Palace during the Silver Jubilee celebrations
Thursday sees the 30th anniversary of one of the worst days in the history of The Troubles.
On 27 August 1979, the Queen's cousin, Lord Louis Mountbatten, was killed in a bomb blast on his boat off County Sligo.
One of the earl's twin grandsons, Nicholas, 14, and Paul Maxwell, 15, a local employed as a boat boy, also died in the explosion.
Later that day, 18 British soldiers were killed as two booby-trap bombs exploded beside Narrow Water Castle, near Warrenpoint in County Down.
It was the highest death toll suffered by the British Army in a single incident in Northern Ireland.
The IRA were behind both attacks.
In a statement at the time the IRA said the killing of Lord Mountbatten was "one of the discriminate ways we can bring to the attention of the English people the continuing occupation of our country."
Another passenger on the boat, the Dowager Lady Brabourne, 82, died the day after the attack.
Lord Mountbatten, who was 79-years-old when he was killed, had traditionally spent summer holidays at Classiebawn Castle near Mullaghmore.
Despite being a member of the Royal family he had never had a bodyguard, and his boat, Shadow V, was left unguarded at the public dock in Mullaghmore.
As the news of Lord Mountbatten's death spread, the first of two bombs exploded in County Down.
The bomb had been planted under hay on a lorry at the side of the road. When it exploded it killed six soldiers who had been travelling past in a four-ton lorry.
As the injured were airlifted from the scene, a second device detonated killing 12 more soldiers who had been taking cover in a nearby gatehouse.
The remaining soldiers were then fired upon and returned fire.
A short time later a local civilian, 28-year-old Michael Hudson was found dead nearby. He had been caught in the crossfire.
Both events will be remembered later in memorial services in Mullaghmore and Narrow Water.
An ecumenical service at the Star of the Sea church in Mullaghmore will be attended by friends and staff of the Mountbattens and the Maxwell family.
In Narrow Water at 1515 BST, the time the first bomb exploded, a service will be held, followed by a wreath-laying ceremony.
The Army will also hold a private memorial services in Northern Ireland and England.