Declassified documents on the mysterious 1956 disappearance of a British naval diver reveal the UK government's interference in the official inquest into his presumed death, and attempts by officials to cover up the truth.

Files unearthed by independent researcher Tom Secker on the April 1956 disappearance of British Royal Navy frogman Lionel "Buster" Crabb OBE while on an underwater spying mission have shed new light on the bizarre and rarely acknowledged episode. Mr. Secker has told Sputnik the files offer few answers, merely further questions.

Crabb, a famed World War II hero, vanished while carrying out a secret operation to spy on a Soviet warship harbored in Portsmouth.

Ever since, the story of his disappearance has been shrouded in intrigue and mystery, spawning innumerable conspiracy theories.

© AP Photo / British naval diver Lieutenant Commander Lionel "Buster" Crabb on board a navy launch in the outer Thames estuary, England, Jan. 14, 1950, where he waits to dive on the hull of British submarine Truculent

Some authors have suggested his operation was discovered by the Soviets, who subsequently killed him — others allege he was in fact conversely recruited by the USSR. Still, others have claimed he was murdered by British authorities, on account of his friendship with members of the infamous "Cambridge Five" who had defected to the USSR in the early years of the Cold War.

The files uncovered by Mr. Secker detail the UK government's interference into the inquest of Crabb's presumed death, an internal inquiry into what happened, and covert attempts by officials to prevent the BBC making a documentary about the story — although the truth of the matter still largely remains a riddle wrapped in an enigma.

Despite close review of the files, Mr. Secker has "no idea" what happened to the frogman.

"The fact there was a separate mission to spy on the Russian warship suggests maybe Crabb wasn't actually spying on the ship after all, and was up to something else. I will also say I don't believe the idea MI5/6 found out he was thinking of defecting and had him killed, because the cover-up would've been much better executed. I get the impression from the files they genuinely didn't know what had gone wrong and were scrambling around telling different lies to different people. This wasn't a coordinated, pre-planned cover-up, it was a reactionary one," Mr. Secker told Sputnik.

Likewise, the independent researcher believes the evidence he was captured by or defected to the Soviets is "pretty thin" — and notes so far nothing has emerged from Soviet archives suggesting they "nabbed him or bumped him off."

"I think this was a screw up — whatever mission Crabb was actually on, it went wrong and he drowned. Though the absence of the body — and the body that washed up obviously not being his — makes that tricky to parse out," Mr. Secker explained.

Disappearing Diver

Crabb rose to prominence due to his expert work in Gilbraltar harbor during World War II, locating and clearing mines placed on ships by Italian divers — he was promoted and awarded the George Medal for his efforts. In 1948 he was demobilized, left the military and became a civilian diver-for-hire, exploring sunken wrecks and locations of interest to pipeline companies.

In 1955, he and a former WW2 associate investigated a Soviet cruiser, trying to identify the technology behind its superior manoeuvrability. It would be his last major assignment before retirement, although he would not be out of work long — the next year, his services were enlisted by MI6.

The UK's overseas spying agency wanted Crabb's help on a domestic operation with an international twist — the April 19, 1956 state visit of Soviet leader Nikita Khrushchev and Foreign Minister Nikolai Bulganin to the UK.

Crabb was dispatched to scrutinize the hull of the cruiser — Ordzhonikidze — that had ferried the two USSR leaders to mainland Britain. An underwater inspection, his MI6 sponsors believed, could reveal details of sonar devices, armour-plating, submarine detection gear, screw dimensions and other features betraying the ship's offensive potential, speed and manoeuvrability.

© Sputnik / "Ordzhonikidze" cruiser in the Indian ocean.

He would never return — and within days was pronounced missing, presumed dead.

Official Lies

Desperate to avoid a major diplomatic crisis, the British Admiralty quickly concocted a cover story, to the effect that Crabb had died testing diving equipment a few miles away from the Soviet ships.

However, 14 months after Crabb's disappearance, a headless, handless body was found floating in the sea near Portsmouth. Crabb's close friend Sydney Knowles, and Crabb's ex-wife, were approached to identify the body, although both refused to confirm it was indeed the legendary diver's corpse. Knowles did so on the basis Crabb had a major scar on his knee but the body he examined didn't — Crabb's ex-wife did so on the basis Crabb had deformed toes that stuck up in an unusual way, while the body found in the sea similarly didn't.

Mr. Secker notes one of the files he has made available states "quite confidently" the Home Office and/or MI5 could persuade the coroner to not ask any potentially embarrassing questions, and to avoid calling witnesses they didn't want to be questioned.

For example, the Navy officer who helped dress Crabb in his gear before he slipped off into the water about 80 yards away from the Russian ship was not questioned — after all, his testimony would if sincere contradict the Admiralty's cover story. Then Head of Naval Intelligence John Inglis told the coroner not to call him as a witness, and instead provided an alternative witness, William John Bostock.

"Bostock knows nothing of the background to the story and will not be able to answer any embarrassing questions even if they are asked," Inglis wrote in a top secret memo.

Likewise, the man who had arrived in Portsmouth with Crabb, his MI6 handler Bernard Smith, was also never called to testify at the inquests.

There are other signs of official manipulation of the inquest process — for instance, the pathologist could not find any specific identifying information, such as a serial number on the diving suit containing the dead body. Nonetheless, the final report concluded a sufficient "chain of coincidences" had been established to certify the cadaver as that of Crabb. An open verdict was reached.

The views and opinions expressed in the article do not necessarily reflect those of Sputnik.