The abuse allegedly took place in 1977, two years before Prince Philip’s uncle was killed by an IRA bomb.
Mr Smyth claims he was abused twice by Lord Mountbatten while he was living at Kincora, a claim which will now be heard at the High Court in Belfast.
A public inquiry five years ago found that at least 39 boys at Kincora had been abused, four decades after three staff members were imprisoned for abusing 11 boys.
The inquiry also criticised the authorities for not taking strong enough action at the time.
Lord Mountbatten has been accused of abusing a young boy
Alleged victim Arthur Smyth
Last year the Police Ombudsman for Northern Ireland criticised the Royal Ulster Constabulary for its “poor response to complaints at the time”, reported the Daily Mail.
Mr Smyth stated he was first abused by William McGrath, a staff member at the home who became known as “the beast of Kincora”.
He said Mr McGrath then introduced him to an “upmarket” stranger in August 1977.
Lord Mountbatten was uncle to Prince Philip
Lord Mountbatten’s name carved into memorial
“And that’s when he took me into that room – downstairs there was a big office, with a big desk and there was a shower.
“[The stranger’s] name was never mentioned in the room. He made me have a shower and then McGrath would come down and get me afterwards.”
Mr Smyth now lives in Australia and claims he only discovered the identity of his attacker after the publicity surrounding his death.
Charles Dance played Lord Mountbatten in The Crown
He added: “You don’t forget who abused you. Trust me. You block it out but you don’t forget.
“I shut it down for years. I felt embarrassed by what had happened but now I want peace.”
Kevin Winters, Mr Smyth’s lawyer, said: “[This is] the first time that someone has stepped forward to take allegations against Lord Mountbatten into a court.
“That decision hasn’t been taken lightly. He understands only too well that it will be a deeply unpopular case with many people, coming as it does within weeks of the passing of the Queen.
“However, litigation involving mental, physical and sex abuse isn’t undertaken to deliberately offend sensitivities.”
Last night a Buckingham Palace spokesperson declined to offer a comment.
Source: EXPRESS CO UK