A top British codebreaker found mysteriously dead last week in his flat had worked with the NSA and British intelligence to intercept e-mail messages that helped convict would-be bombers in the U.K., according to a news report.

Gareth Williams, 31, made repeated visits to the U.S. to meet with the National Security Agency and worked closely with British and U.S. spy agencies to intercept and examine communications that passed between an al Qaeda official in Pakistan and three men who were convicted last year of plotting to bomb transcontinental flights, according to the British paper the Mirror.

Williams, described by those who knew him as a "math genius," worked for the Government Communications Headquarters (GCHQ) helping to break coded Taliban communications, among other things. He was just completing a year-long stint with MI6, Britain's secret intelligence service, when his body was found stuffed into a duffel bag in his bathtub. He'd been dead for at least a week. His mobile phone and a number of SIM cards were laid out on a table near the body, according to news reports. There were no signs of forced entry to the apartment and no signs of a struggle.

Initial news stories indicated Williams had been stabbed, but police have since disputed that information, noting that – other than being stuffed into a duffel bag – there were no obvious signs of foul play. A toxicology report is expected Tuesday.

Investigators say they haven't ruled out the possibility that the codebreaker was killed over something related to his work. Rumors that sexual bondage equipment was found in his apartment were also nixed by police, who said the rumors were untrue and they found no evidence yet to suggest that anything in Williams' personal life led to his death.

Williams, an avid cyclist, lived in an apartment in Pimlico in central London that was reportedly part of a network of flats registered to an offshore front company and rented out to GCHQ workers. He is believed to have returned from a trip abroad on August 11. He was last seen alive on August 15, eight days before his body was found.

Williams flew up to four times a year to the U.S. to the NSA's headquarters at Fort Meade HQ, according to the Mirror. His uncle, Michael Hughes, told the paper that Williams would mysteriously disappear for three or four weeks.

"The trips were very hush-hush," Hughes said. "They were so secret that I only recently found out about them - and we're a very close family. It had become part of his job in the past few years. His last trip out there was a few weeks ago, but he was regularly back and forth."

Williams was said to have worked with the NSA on e-mails intercepted between Abdullah Ahmed Ali and Assad Sarwar and Rashid Rauf, a British national in Pakistan who was allegedly director of European operations for al Qaeda. The e-mails, intercepted by the NSA in 2006, allegedly contained coded messages.

The NSA shared the e-mails with British prosecutors but wouldn't allow them to use the evidence in an early trial of the suspects out of fear of tipping off Rauf that he was under surveillance. It was only after Rauf was reportedly killed in a U.S. drone attack that the NSA allowed prosecutors to use the e-mails to convict the other suspects. It's never been known whether the NSA intercepted the messages overseas or siphoned them as they passed through internet nodes on U.S. soil as part of the NSA's controversial and unconstitutional warrantless wiretapping program.

An unidentified Western intelligence source told the Mirror that Williams' job would have had him participating in "crucial high-level meetings with American intelligence officers. His job would have been crucial to the security of the UK and our interests abroad - and also to America and Europe.

"Although not particularly high up the GCHQ ladder, the importance of his role should not be underestimated. The man was a mathematical genius."

His landlady, Jenny Elliott, told the Telegraph, "Occasionally you could hear tapes whirring from his flat, which must have been audio cassettes he used for work, but he never told me what they were."

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