A former Armed Forces minister who served under Captain Robert Nairac has urged the soldier's IRA killers to reveal where his body is buried.
Sir Mike Penning, a former Grenadier Guardsman, said those who carried out the murder were "cowards".
Captain Nairac was abducted by the IRA while on an undercover operation in a pub in south Armagh in 1977.
It is believed he was beaten and then shot dead, but his remains have never been found.
Sir Mike (inset, top), who is now Conservative MP for Hemel Hempstead, remembered his commanding officer as an "incredibly brave" man. "He had a real presence and to us troops was a great Captain and we would follow him anywhere," he said,in an article for the PoliticsHome website.
Nairac (inset, below) - described by some as a maverick - was 28 when he disappeared on the evening of Saturday May 14 1977.
He had been undercover, drinking and singing republican folk songs in the Three Steps Inn in Dromintee, south Armagh.
As he left the bar, he was attacked in the car park and abducted.
The IRA later said he had been shot.
Despite wide- ranging searches at the time, his body was not recovered.
Last Tuesday, to coincide with the 41st anniversary of his disappearance, Sir Mike raised a Point of Order in the House of Commons.
Writing on PoliticsHome yesterday, he said his former captain was among those who paid with their life to help bring peace to Northern Ireland.
"It is often reported that he was either unbelievably brave or incredibly reckless. Without doubt, he was certainly a bit of a maverick," he wrote.
"It appears that on that fateful night he was acting purely alone, without the Army knowing what he was doing or where he was, but I don't buy the notion that he was reckless.
"He was far too clever and calculating to be that.
"He would have carefully calculated the risks of what he was doing and weighed them against the need for intelligence.
"On that fateful night in May 1977, however, he paid with his life."
Nairac is one of the so-called Disappeared - people abducted, murdered and secretly buried by republicans during the Troubles.
He is one of three victims whose remains have never been recovered.
Sir Mike said it was time for those who killed Nairac to come forward and reveal his whereabouts.
He added: "The cowards who almost certainly tortured him following his abduction and then murdered him in cold blood, know where he lies.
"He, and so many others, gave so much for the peace that Northern Ireland enjoys today. But for Captain Robert Nairac's family, there cannot be any true peace until they know the truth and can lay him to rest.
"To me, he was most definitely an incredibly brave young man. Isn't it time my former Captain can rest in peace?"