The only member of the Miami Showband not present at the scene of the massacre is suing over alleged state collusion in the loyalist paramilitary attack.
Ray Millar described himself as the “forgotten man” of the atrocity where three of his bandmates were murdered following a performance in July 1975.
The drummer has issued High Court proceedings against the Ministry of Defence and PSNI, claiming damages for post-traumatic stress disorder as a secondary victim.
He said: “Fate intervened that terrible night and I went home after the gig, but I have had to relive the awful experience daily.”
One of Ireland's most popular cabaret acts, the rest of the Miami Showband were targeted as they returned to Dublin from a concert in Banbridge.
A fake army patrol made up of UDR soldiers and UVF members stopped them at a bogus checkpoint outside Newry, Co Down.
Band members were made to line up at the side of the road while attempts were made to hide a bomb on their tour bus.
The device exploded prematurely, killing some of the would-be bombers.
Their terrorist accomplices then opened fire on the band, murdering lead singer Fran O'Toole, guitarist Tony Geraghty and trumpeter Brian McCoy.
Two other musicians, Des McAlea and Stephen Travers, were also injured but survived the attack.
Mr Millar had left Banbridge separately from his bandmates and only learned about the killings after he got home.
An Historical Enquiries Team report into the atrocity raised collusion concerns around the involvement of an RUC Special Branch agent.
It found that notorious UVF boss Robin 'The Jackal' Jackson had been linked to one of the murder weapons by fingerprints.
Jackson, a one-time UDR member who died in 1998, claimed in police interviews he had been tipped off by a senior police officer to lie low after the killings.
He went on trial charged with possession of a silencer attached to a pistol used in the murders but was subsequently acquitted.
Two serving members of the UDR were, however, eventually convicted for their part in the attack.
In 2021 other members of the Miami Showband and relatives of those murdered received nearly £1.5m in total damages to settle claims against the MoD and PSNI without any admission of liability.
Mr Millar has now issued a similar writ for alleged negligence and misfeasance in public office.
Papers lodged at the High Court claim the planning, preparation, execution and subsequent concealment of state involvement in the killing of his bandmates resulted in psychiatric injury and financial loss.
Mr Millar stressed his thoughts will always be with those who lost their lives, their families and the other survivors.
“It's absolutely terrible what happened and despite the passage of time the full horror of it all still shocks everyone,” he said.
“However I feel I am a sort of forgotten man of the Miami Showband.”
He added: “I am taking this case now because I believe that I am also a victim of ‘state-loyalist’ collusion and I’ve never been recognised as such.
“I know there are complex and sensitive legal issues around it but all I want is a wee bit of recognition.’’
His solicitor, Padraig McIlkenny of KRW Law, expressed confidence that he will be able to successfully sue as a secondary victim not present at the scene.
Mr McIlkenny also claimed: “His case is precisely the sort of legal action which the state is determined to prevent.
“Equally we are confident the courts will engage fairly on any political and legal state attempt to shut down access to the courts.”