A former Royal Navy sailor overheard a conversation that suggested a submarine was involved in the sinking of the Gaul trawler, an inquiry has heard.
Mr Barron claims he overheard the concerns of a warrant officer
Derek Barron was giving evidence at an inquiry into the 1974 sinking in the Barents Sea, in which 36 seamen died.
Mr Barron was at a training course when he overheard a warrant officer discuss the tragedy. The "inference" was that a UK submarine was responsible, he said.
The MoD said its nearest submarine was more than 1,000 nautical miles away.
Mr Barron told the inquiry he believed the vessel involved was The Resolution, a nuclear submarine used to patrol the Barents Sea at the height of the Cold War.
He was on a training course at HMS Dolphin in Hampshire in 1983 when he heard the warrant officer discuss the Gaul with an Army officer in a mess.
"I don't recall any description of any entanglement or anything on those lines," said Mr Barron.
"It was a long time ago. I remember him saying he was on a sub, they were there when the Gaul sank. He was distressed because they could not surface for any survivors. These are the only things I could say for certain."
Wreck Commissioner Mr Justice Steel reconvened the inquiry in Hull to hear fresh evidence from the Ministry of Defence and Mr Barron.
A statement from the chief engineer of a Swedish vessel, the Anaris, which was in the Barents Sea in February 1974, was also heard.
Tobjorn Kirksaether, a Norwegian who was aged 50 at the time of the tragedy, said the tanker had sailed close to the Gaul as she was sinking in a fierce storm.
He described her final moments as she struggled to keep afloat in three metre waves.
He said: "I could tell there was a problem on board (the Gaul). The Gaul was simply being thrown around. Just after that she was buried by a large amount of water. The drama lasted barely a few seconds."
Asked if his crew searched for the trawler, he said: "There was no vessel to search for."
However, Nigel Meeson QC, for the Attorney General, said other crew members from The Anaris could not remember the Gaul's position or any mention of her.
He said: "What is surprising is that somebody who saw a ship sink just shrugs his shoulders and doesn't bother to tell anybody about it."
The Gaul sank in stormy weather off the coast of Norway, without any distress signal being sent.
Many theories have since been put forward, including that it was sunk by the Soviet Union because it was acting as a spy vessel.
But Attorney General Lord Goldsmith told the inquiry there was no evidence the Gaul was involved in spying, which was backed up by an MI6 officer who also gave evidence.
The wreck of the Gaul was located in 1997 and two years later Deputy Prime Minister John Prescott ordered the reopening of the 1974 inquiry into the sinking, which originally concluded it had been swamped by stormy seas.
After the one-day sitting, the commissioner, Mr Justice Steel, will complete his report, which is expected to be published later this year.