A ruthless ex-IRA commander has sensationally confessed to The Mail on Sunday that he was behind the assassination of King Charles’s beloved great-uncle.

In an astonishing admission set to cause huge pain to Charles, Michael Hayes callously boasted that he designed the explosive device that killed Lord Mountbatten, and masterminded the atrocity.

Lord Mountbatten – a mentor to both Prince Philip and the then Prince Charles – was murdered aged 79 when the IRA blew up his pleasure boat during a holiday at his summer home in Co Sligo, on the west coast of the Republic of Ireland, in August 1979.

Only one member of the IRA was ever convicted of the atrocity. Thomas McMahon was arrested on the day of the blast and jailed for life but later released under the Good Friday Agreement.

But now, after being approached by a MoS reporter, Hayes has bragged: ‘I blew up Earl Mountbatten.’

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Michael Hayes (pictured) callously boasted that he designed the explosive device that killed Lord Mountbatten, and masterminded the atrocity

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Hayes (pictured) said that he did not regret killing Lord Mountbatten and coldly described the two teenage boys who died as ‘casualties of war’

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Lord Mountbatten – a mentor to both Prince Philip and the then Prince Charles – who was murdered aged 79

Killed alongside the earl were his grandson Nicholas, 14; Doreen Brabourne, 83, Nicholas’s grandmother; and crewman Paul Maxwell, 15, of Enniskillen.

Legal experts this weekend told the MoS that Hayes’s admission made him liable for prosecution for the murders, if the Irish police and Director of Public Prosecution decided to pursue him.

Hayes said that he did not regret killing Lord Mountbatten and coldly described the two teenage boys who died as ‘casualties of war’.

As Buckingham Palace last night declined to comment, Ian Paisley Jr, the Democratic Unionist Party MP for North Antrim in Ulster, called for the Garda Síochána, the police service in the Republic of Ireland, to ‘immediately’ investigate Hayes.

‘The sensational, shocking and blood-curdling statement by a self-confessed, cold-blooded murderer ought to be immediately investigated by the police and the man brought to justice,’ he said.

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Queen Elizabeth II pictured chatting with Lord Louis Mountbatten at the Guards Polo Club on June 1 1975

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The IRA blew up Mountbatten’s pleasure boat during a holiday at his summer home in Co Sligo, on the west coast of the Republic of Ireland. Pictured: The wreckage after the explosion

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Legal experts this weekend told the MoS that Hayes’s admission made him liable for prosecution for the murders. Pictured: Part of the wreakage of Lord Mountbattens boat the Shadow V, circa August 1979

The brutal killing of Lord Mountbatten, who was affectionately known as ‘Uncle Dickie’ by the Royal Family, affected Charles deeply. In his diary, the 31-year old Prince of Wales wrote of ‘agony, disbelief, a kind of wretched numbness’. But in 2015 Charles showed forgiveness, shaking hands with Sinn Fein leader Gerry Adams after travelling to Ireland to see where Mountbatten died.

Hayes, a grandfather who lives alone in Dublin, was previously named as one of four men behind the 1974 IRA Birmingham bombings and has taken what he called ‘collective responsibility’ for all of the IRA’s actions in England.

But he has never before linked himself to the murder of Lord Mountbatten and the other victims who died when a remote-controlled 50lb bomb ripped through the hull of the Shadow V. Speaking to a MoS reporter, Hayes revealed that he was McMahon’s ‘commanding officer’. He said: ‘Tom McMahon, he was only a participant. I am an explosives expert, I am renowned. I was trained in Libya. I trained there as an explosives expert.’

Asked if he was saying that he was the man who designed the bomb, he boasted: ‘Yes, I blew him up. McMahon put it on his boat … I planned everything, I am commander in chief. ‘

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Hayes has never before linked himself to the murder of Lord Mountbatten and the other victims who died when a remote-controlled 50lb bomb ripped through the hull of the Shadow V. Pictured: Debris of the boat following the blast

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The brutal killing of Lord Mountbatten (pictured), who was affectionately known as ‘Uncle Dickie’ by the Royal Family, affected Charles deeply

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Prince Charles is pictured with Lord Louis Mountbatten at a polo match holding pint of beer

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Earl Mountbatten’s coffin is carried during his funeral following his death at the age of 79

An alleged IRA accomplice, Francis McGirl, was also arrested on the day of the attack but he was later acquitted. He died in a farming accident in 1995.

Hayes confirmed to the MoS that he was also in County Sligo at the time of the bombing, adding: ‘Francis McGirl made a b******s of it. I blew up Earl Mountbatten in Sligo, but I had a justification, he’d come to my country… Look at the Famine … are we to forget that? The Black and Tans? He came to my country and murdered my people and I fought back. I hit them back.’

There is no bar to prosecution of Troubles-era offences and any immunity as part of the Good Friday Agreement only applies to convictions handed down for crimes that have been prosecuted before the courts. A legal source said: ‘This person [Hayes] could very reasonably be prosecuted…’

Asked if detectives would investigate Hayes, a Garda spokesman said: ‘As a matter of public record, two persons were prosecuted in respect of the murder of Lord Mountbatten. One individual was acquitted and a second individual served a sentence of imprisonment and was subsequently released pursuant to the Good Friday Agreement.’ But when asked if he feared prosecution, Hayes said: ‘No, I fought a war, I was justified.’ Asked if he regretted the explosion he said: ‘Blowing up Mountbatten? No.’

But asked about the two boys murdered that day, he replied: ‘Them children were not supposed to be on the boat in the first place.

Although, sickeningly, he called the youngsters ‘casualties of war’, he conceded: ‘Yes, I regret that, that wasn’t meant to happen. I’m a father. I’m not made of stone. I was sickened, I cried.’

Last night Mary Hornsey, 84, mother of young victim Paul Maxwell, said she would welcome a police probe into Hayes’ claims ‘to see whether or not he was involved, whether he really was the commander who did give the order’.

She added: ‘I think we would require justice, not revenge.’ Speaking of the loss of her son, she explained: ‘It’s something that never goes away.’

Senior Tory MP Sir Iain Duncan Smith, who served in Northern Ireland with the Scots Guards, also urged the Garda to investigate Hayes’s claim, adding: ‘It’s important to get to the truth.’