A MYSTERIOUS letter provided a bizarre twist in a inquiry into the sinking of a trawler yesterday.

But relatives of the 36 men who perished in the Gaul disaster claim the probe has brought them no closer to the truth.

The Hull-docked vessel sank off the coast of Norway in 1974 amid rumours it was involved in spying on the Soviet navy, a claim the Ministry of Defence has always denied.

Sheila Doone, of Sackville Street, Brierfield, whose husband, John, was a radio operator on the trawler, is among a group of relatives who have campaigned for the truth about the Gaul's sinking.

Now in its sixth week, the inquiry is hearing final submissions before Wreck Commissioner, Mr Justice Steel, makes his conclusions. But despite the mountain of evidence, relatives of the seamen who died feel many questions remain unanswered.

Yesterday's hearing witnessed a letter from an anonymous man claiming to be a Royal Navy chief petty officer from a nuclear submarine was handed to the inquiry.

In the letter, he alleged he had overheard a conversation in which an officer claimed a submarine patrolling the Barents Sea in 1974 had hit a trawler, dragging it until it sank. He said the submarine was not allowed to search for survivors as it was under orders to remain undetected.

Mr Justice Steel did not address the contents of the letter, nor did inquiry barrister Nigel Meeson QC. But relatives speaking outside the inquiry demanded the letter's claims be investigated

Ken Collier, whose father Stan was killed in the tragedy, said: "We've had letters like this over the past 30 years. How do you know what to believe? But you have to at least examine the possibility of this. We know similar incidents involving submarines sinking vessels like these have happened before."

Beryl Betts, chair of the Gaul Families' Association, whose brother Billy Jones died, said: "This inquiry is going to say it sank because of the duff and offal chutes, which is absolute rubbish."

Mr Meeson finished his closing submissions by concluding the vessel sank after experiencing steering problems and taking on board a large amount of water through the open duff and offal chutes.

He dismissed as improbable theories the tragedy was a result of a cable snagging, fire, collision, explosion, ice or grounding. He also quashed the theory the ship was boarded by Russians and deliberately sabotaged.

Mr Meeson said: "The most probable loss is accumulated water in the factory deck and the vessel suffering a roll to starboard, which disabled the crew."

He made recommendations to prevent a similar tragedy, including fitting water level alarms and CCTV in the factory decks of trawlers. He also suggested a warning light in the bridge to alert skippers when hatches were left open.