'He swam out to the Russian vessel and was never seen alive again': The Cold War spy mystery of the 'vanishing frogman'

In 1956, Royal Navy Commander "Buster" Crabb disappeared in murky circumstances during a visit to the UK by Soviet leader Nikita Khruschev. In 2006, the BBC's Michael Buchanan read the newly declassified files that detailed Crabb's unofficial secret mission – and how the government tried to cover it up.

It was on 9 May 1956, 68 years ago this week, that UK Prime Minister Sir Anthony Eden finally succumbed to press pressure and international embarrassment, and ordered an enquiry into the mysterious disappearance of Royal Navy diver Commander Lionel "Buster" Crabb.

The decorated frogman had vanished during a goodwill visit to the UK by the Soviet leadership at the height of Cold War tensions. When word leaked that Crabb had gone missing, The Admiralty, the government department responsible for the Navy, issued a vague statement that the diver had been testing underwater equipment at Stokes Bay on the Hampshire coast and was presumed drowned.

But the story fell apart when the visiting Russians accused their hosts of espionage. The Soviets claimed that they had seen a frogman near the Ordzhonikidze – the ship that had brought the Soviet leader Nikita Khruschev to the UK – while it was docked in Portsmouth Harbour. Despite questions being asked repeatedly in Parliament, Eden refused to say more, claiming: "It would not be in the public interest to disclose the circumstances in which Commander Crabb is presumed to have met his death." The government's stonewalling merely heightened suspicions that Crabb had been on a covert spy mission.

Fourteen months after Crabb vanished, a headless, handless body in a diving suit was found by fishermen in Chichester Harbour on the south coast of England. Its lack of fingerprints and teeth made the mutilated body difficult to identify, but a later inquest ruled that it was Crabb. The whole episode publicly embarrassed Eden and wrecked his attempts to develop a more friendly relationship with a post-Stalin Soviet Union. 

When he disappeared in 1956, Crabb was well known for his daring underwater exploits. Nicknamed "Buster", after the US Olympic swimmer and actor Buster Crabbe, who had risen to fame in the 1930s, he was an expert in underwater bomb disposal. His bravery during World War Two had earned him the George Medal for removing Italian limpet mines from British warships at Malta, and an Order of the British Empire (OBE) for his mine clearance work at Livorno in Italy. His wartime amphibious adventures would later be fictionalised in a 1958 film, The Silent Enemy, with Crabb being played by Laurence Harvey. And even after he was officially demobbed in 1947, he continued diving for the military in various capacities, including investigating sunken submarines.

For decades following the frogman's disappearance, the UK government staunchly maintained its silence on the incident. It would only be from 2006 onwards, when due to Freedom of Information requests by the BBC, and classified documents being made public under the 50-year rule, that the murky circumstances of Crabb's ill-fated final dive began to emerge.

The declassified files showed that, from the start, the UK's security services were keen to use the opportunity of Khruschev's visit to gather intelligence on their Cold War opponents. They suggested hiding microphones in Claridge's hotel, which the Soviet leadership intended to use as their headquarters during their stay. But the prime minister expressly ruled out the idea and made "clear that adventures of a similar nature were forbidden". 

Despite this, MI6 recruited Crabb to undertake an "unofficial enterprise" to investigate the Russian ship Ordzhonikidze. The exact nature of his mission is still unclear, but the ex-MI5 officer Peter Wright suggested in his book Spycatcher (1987) that it was to examine and photograph the ship's advanced propeller design.

Two days before the mission, Crabb and another MI6 agent, who went by the name Bernard Smith, checked into the Sally Port hotel in Portsmouth. On the evening of 17 April 1956, Crabb met with a military colleague in a local pub. This colleague, whose name was deleted from the file, was a Royal Navy lieutenant commander who agreed to help Crabb get into Portsmouth Harbour for his final dive. In 2006, the BBC's Michael Buchanan got the chance to examine the previously classified sworn statement by "the last man to see Crabb alive".

"He says he was approached by the commander a couple of days before his final dive and asked 'if I would be prepared to assist him, entirely unofficially and in a strictly private capacity, in connection with a dive he was taking a day or two later'. He goes on to say under no account was this man to contact any responsible naval authority," said Buchanan.

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Just before 07:00 on 19 April, the unnamed lieutenant commander went with Crabb to Portsmouth Harbour, and helped him dress and check his equipment. Crabb then swam out to the Russian vessel, and was never seen alive again. The Royal Navy made no attempt to look for the missing frogman for fear of alerting the Ordzhonikidze's crew. "The documents further reveal that no search and rescue efforts were made for Crabb as it was not a bonafide operation," said Buchanan. "And they detailed the extensive efforts made by [the Admiralty] to ensure they weren't implicated in a botched mission they knew nothing about."

The intelligence services surmised that Crabb must have either been captured by the Soviets, been destroyed by Russian "countermeasures", or suffered a "natural mishap". Smith, the MI6 agent, removed Crabb's belongings and checked out of the Sally Port hotel. A few days later, the police removed the pages with their details from the Sally Port's register, which only served to fuel suspicions of a covert mission. Under pressure from MI6 and the government, the Admiralty hastily concocted the spurious story that Crabb had gone missing during a test in Stokes Bay.

Records of meetings show the panic at the highest levels of government. Officials feared that if a body was found, the Soviets could use Crabb's death for propaganda purposes. National Archives' Howard Davis told the BBC in 2006 that the file "makes it perfectly clear that this wasn't an Admiralty operation; they had nothing to do with it and we see them trying to construct a story that they can plausibly tell to face the inevitable questions from the press".

But despite the release of some of the government's classified documents, exactly what happened to the diver that day in 1956 is still unknown. In 1990, Joseph Zwerkin, a former Soviet naval intelligence agent, claimed that a Soviet sniper on the Ordzhonikidze's deck had spotted the diver in the water and shot him. In 2007, a 74-year-old former Russian frogman, Eduard Koltsov, claimed that he slashed Crabb's throat in an underwater fight after catching him attaching a mine to Ordzhonikidze.

It has also been suggested that as Crabb was an associate of Sir Anthony Blunt, who was unmasked as a Soviet spy in 1979, he could even have defected. Nicholas Elliott, a former senior MI6 agent who was rumoured to be involved in Crabb's final dive, believed that the 47-year-old diver, who was known for his fondness for whiskey and cigarettes, had succumbed to oxygen poisoning or a heart attack as a result of his exertions while underwater.

It may be some time before more details of Crabb's fate come to light. While some papers concerning the affair have been released into the public domain, others have had their classified status extended by the government and are not scheduled for release until 2057.

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