The boss of a British spy whose naked and decomposing body was found locked in a sports bag waited for a week before raising the alarm after his colleague went missing, an inquest into the codebreaker's mysterious death was told Wednesday.

Cryptology expert Gareth Williams, 31, worked for Britain's secret eavesdropping service GCHQ, but was attached to the country's MI6 overseas spy agency when he was discovered dead in August 2010 under bizarre circumstances at his central London apartment.

Police have made no arrests in the case and are still not certain how exactly Williams died. The spy's family rejects British authorities' claim that his death was unconnected to his intelligence work.

An inquest charged with deducing how and when Williams died heard anonymous evidence Wednesday from three British spies who acknowledged it took seven days after the codebreaker first failed to show up for work before his MI6 boss contacted his family.

The codebreaker's direct manager, a witness identified only as "G," said Williams shared a small office with three other people and had carried out some operational work on behalf of the spy agency in addition to his technical work.

Williams was a "quiet intellectual" who was almost always punctual and had never been absent from work through illness, his manager said.

"He was clearly very clever but there were those that say he was shy, an introvert and a very quiet person," the manager told the inquest.

Shortly before his death, Williams had visited Las Vegas as part of his duties but had been due at work in London on August 16. When he didn't arrive, the manager said he and other colleagues assumed William was having transport problems.

A day later, with still no signs of the spy, the manager said he called Williams but received no response from his phone. By August 20, the manager visited the apartment where William lived but failed to raise any response.

Coroner Fiona Wilcox told the manager she was "really struggling to understand why you took no action at this point."

The witness told the inquest hearing that he had a "gut feeling that he was away doing something that I was not made aware of."

Only on August 23 did the spy's manager raise the alarm with senior bosses and the spy's family. His body was found later that day.

"In hindsight, knowing what I know now, should I have taken action? Absolutely," the manager acknowledged, giving his testimony from behind a screen to protect his identity.

A lawyer for the spy's family said previously that relatives suspect an "unknown third party" may have tampered with the scene after Williams died, or interfered with other evidence that could help explain how he died.

In other evidence, a former landlady who rented out an apartment to Williams in an annex of her house in Cheltenham, southern England — where GCHQ is based — described how she once found the codebreaker tied to his bed.

Jennifer Elliot's written testimony was read out at the hearing, detailing how she and her husband responded to Williams calling for help in the middle of the night.

"We went upstairs and found him lying in his bed with both hands tied with material attached at the headboard," Elliot said.

Elliott said Williams had explained that he tied himself up "to see if he could get free" but she and her husband had concluded the incident was "more likely to be sexual than escapology."

Police have investigated whether the spy's death happened in a bondage-related sex game that had gone wrong.