SOURCE: BBC (7-12-06)
Lionel "Buster" Crabb vanished while spying on Soviet warships visiting the city at the height of the Cold War.
The frogman's fate has remained one of the country's most closely-guarded secrets, but the BBC has obtained the report into his final mission on 19 April, 1956.
The secret document was the subject of a Freedom Of Information application by BBC Radio Solent.
It shows that Crabb's intelligence service handlers did not take proper precautions to protect him or the secrecy of the mission.
When he failed to reappear they decided not to carry out a full search for fear of alerting the crew of the cruiser Ordzhonikidze which had brought Nikita Khrushchev on a diplomatic visit.