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A WELSH spy’s bizarre death may be linked to a cyber attack on Iran’s controversial nuclear power plant, an espionage expert has claimed.

Gareth Williams’ death remains a mystery.

The MI6 man’s naked body was found in a padlocked holdall at his London flat on August 23.

Tests found no traces of poison, drugs or alcohol in his body and the Metropolitan Police and the FBI are continuing to investigate.

Now, Ammanford-born Gordon Thomas – former war correspondent, documentary maker and the author of books on international espionage – has a new theory.

He believes Stuxnet, the world’s first “cyber super weapon”, could be behind Williams’ death.

Stuxnet is a computer virus, the most sophisticated “worm” ever created, which is already in 45,000 networks worldwide.

It attacks by reprogramming software to give any industrial machinery new instructions.

Iran’s controversial Bushehr nuclear power plant has been badly hit. The country has been bombarded by the virus, with nearly 60% of all infected PCs worldwide found there.

But no-one knows who created the virus.

Mr Thomas, author of Inside British Intelligence: 100 Years of MI5 and MI6, said Stuxnet was the kind of project Mr Williams, a 30-year-old maths genius from Anglesey, would have been involved in.

He said: “Williams was at the cutting edge of computer technology.

“His mathematical brain made him a vital tool in the fight against terrorism and cyber warfare.

“In 2000, Williams left his Cambridge University course in advanced mathematics because he had already learned all he could.

“By then, he’d been ‘tapped’ – recruited by GCHQ scouts, who tour universities looking for talent.

“He worked at the Super Computer Centre, speeding up data encryption.

“In 2003, he was at Menwith Hill, the ultra-secret RAF station in Yorkshire.

“In 2006, Williams spent time at Fort Meade in Maryland, home of the United States’ National Security Agency.

“No wonder the FBI is examining his death.

“A further sign of Williams’ importance was his flat at 36 Alderney Street – a high-security Pimlico apartment MI6 would have previously used to debrief its agents or a defector.

“Williams would have been cautioned about who he was allowed to entertain at home.

“But if he was involved in looking at Stuxnet, and I believe he could have been, he would have been a potential target.

“Intelligence agencies from around the world would want to know how to stop it, how to start it and some would want revenge for damage done by it.”

Another of Thomas’ books, Gideon’s Spies: Mossad’s Secret Warriors, became a major documentary for Channel Four called The Spy Machine, which he wrote and narrated.

Now living in Bath, he said Williams, close to finishing a one-year secondment from CCHQ in Cheltenham to MI6, could have been eliminated or become the target of a pressure campaign, adding: “Stuxnet is serious business.”

The head of MI6, Sir John Sawers, says the death is a police matter.

The Metropolitan Police consider his death “suspicious and unexplained”.