Salisbury, who was employed at the Naval Dockyard in Plymouth for most of the inter-war years, was a Communist dismissed from his employment over alleged involvement in the sabotage of naval vessels in Devonport, though there was never enough evidence to try him on this charge and it is doubtful that such activity was ever sanctioned by the Party. That an open Communist might also engage in sabotage never seemed to have occurred to the security forces. Yet Salisbury first came to their attention in 1931, when he was noted distributing Communist propaganda to other workers and naval servicemen, and was observed making contact with discharged naval ratings.
Plymouth City Constabulary kept a close watch on his activities and wrote regular reports to the Security Service. Plymouth Police refered to Salisbury as "a poisonous reptile". A watch was mounted on his correspondence, and he was frequently tailed on train journeys to London. A dockyard police informant also provided information.
MI5 even collected a report of a conversation with Salisbury where he gaves his own account of being constantly tailed. When the Royal Fleet Auxilliary ship War Afridi was sabotaged in 1933, Salisbury was noted as being believed to have worked on the ship at the right time to be involved. This close watch on Salisbury, his family and contacts continued.
In 1935, it was claimed that the submarine HMS Oberon was sabotaged. Salisbury was known to have worked on the boat at the time. Though Salisbury could not be clearly placed as working on HMS Royal Oak when it too was sabotaged, he was supposed to have known facts of the case that were not otherwise public knowledge. The evidence was enough for the Admiralty to order his interrogation. Salisbury was finally discharged from the dockyard on 1 February 1936. A close watch continued to be kept on him and his family even into well the 1950s.
Source: National Archives