Crabb and his mother Beatrice and father Hugh lived in poverty. Nicknamed “Buster,” Crabb served as a merchant seaman as World War II began and was commissioned into the Royal Nay Patrol service in 1941 after first serving as an army gunner. Because of an eye injury he was unable to travel to sea and volunteered for the dangerous task of mine and bomb disposal. He was assigned to Gibraltar in 1942 and aided other Navy divers in protecting British ships against Italian saboteurs. Italian frogmen ambitiously sought to install limpet mines to the hulls of British ships.
Initially Crabb was assigned to disarm bomb removed from ships, but he eventually asked to be trained as a diver. He was a quickly learner and received numerous commendations, including a George Medal. He was eventually promoted to the rank of Lieutenant Commander. Became the Principal Diving Officer for Northern Italy in 1943. A few years later he was stationed to Palestine and in 1948 he left the Royal Navy.
In 1952 Crabb returned to active duty and was assigned to frogman duties in various ports. He searched and investigated sunken Royal Navy submarines. Married Margaret Player and continued on as a frogman, and in 1955 worked with another frogman, Sydney Knowles, investigated the hull of a Soviet ship, the Sverdlov.
Crabb was recruited by MI6 and on April 19, 1956, he was assigned to perform surveillance on a Soviet cruiser, . The cruiser, the Ordzhonikidze, had carried Soviet premier Nikolai Bulganin and future premier Nikita Khrushchev into Portsmouth Harbor in England on a diplomatic mission. Crabb was inspecting the hull of the ship but did not check in with his MI6 contact. He was never seen again.
Speculation swirled around Crabb’s disappearance. Rumors abounded that he was captured by the Soviets, that he was a double-agent and defected to the Soviet union and even that he was shot by the British services. However, in 1990, Joseph Zwerkin, a former Soviet Intelligence agent explaiend that Soviet security saw Crabb as he was inspecting the Ordzhonikidze and a sniper shot him in the water. The fallout from the disappearance was immense. Crabb was operating under the guidance of MI6 which is governed to operate outside of Britain while MI5 operates within the country. Although MI6 attempted to cover-up the operation. British Prime Minister Anthony Eden forced the resignation of John Alexander Sinclair, the Director-General of MI6.
British government documents related to the Crabb case will not be released until 2057.