This publication sets out the report of the re-opened formal investigation into the loss of FV Gaul, a fishing trawler last seen off the Norwegian coast in February 1974, resulting in the loss of its 36 crewmen. The original formal inquiry concluded that the vessel had foundered and capsized, without making any distress calls, after being battered by heavy seas. The report is divided into two sections. The first part includes: a brief historical account of the loss of FV Gaul, and the concerns surrounding its loss; the vessel's design features, the regulatory measures in place at the time it was built and its service history; the experience of its skipper and crew; a detailed account of its last voyage and the search and investigation undertaken after it went down; and examination of concerns that its loss was due to involvement in espionage activities during the Cold War, including evidence from two members of the Security Services. The second section looks at: the findings of the maritime accident investigation undertaken in 1998 and the underwater survey undertaken in 2002, including technology used; examination of possible theories to explain the cause of the loss, including whether the vessel was fishing at the time of the loss, whether a snagged submarine cable could have caused the incident, and the prevailing weather and sea conditions. The report concludes that it is probable FV Gaul capsized amid heavy seas, when water ran down open waste chutes and flooded its lower decks, rapidly disabling the crew who were subsequently unable to send a distress call. The report, therefore, rules out other explanations for the loss of the vessel such as collision, seizure by the Russians or any other hostile force, or being pulled down by a submarine due to a snagged fishing net.