The captain and his ship Endurance played a vital part in the 1982 South Atlantic conflict.
But he incurred the wrath of the Establishment by saying his warnings of an escalation of tension in the area before the invasion had been ignored.
In January 1982, when the ship visited the Argentinian port of Ushuaia, he was told by an Argentine naval officer that he was in "the Malvinas war zone".
When he asked who the enemy was, he was told: "You".
He was also warned by an Argentine captain over a glass of brandy that an invasion was imminent. Both incidents, he said, were reported but ignored by officials.
He also said he was brushed off by Navy HQ when he phoned during the conflict to clarify the rules of engagement. He was told to ring again after 2pm when the relevant official would be back from lunch.
The son of a Navy man, Capt Barker retired from the service in 1988. He went on to write novels, including Red Ice, a thriller set in the South Atlantic, and Beyond Endurance, an account of the conflict. Capt Barker, who died after a long illness, leaves a wife, Jennifer, and four children. Obituary, page 16