Investigators are still days away from finding out the exact cause of death of British code-breaker Gareth Williams, police said yesterday.

The complicated nature of the tests currently being carried out means it could be well into next week before police are able to piece together how the maths genius died.

A post mortem examination undertaken earlier this week proved inconclusive and officers are still days away from determining if he was asphyxiated, poisoned or if drugs or alcohol were present in his system.

He was last seen alive eight days before his corpse was found stuffed in a bag at his flat.

A confirmed sighting of Williams, 30, was made on 15 August in London, officers said.

But police would not say today whether the sighting was made on CCTV or came from another source.

The investigation is being led by the Met's Homicide Command with the security-vetted Counter Terror Command (SO15) also playing a lesser role in proceedings.

Scotland Yard played down reports that thousands of pounds had passed through Williams' bank account shortly before his death as "pure speculation".

It was reported that three sums of £2,000 were paid into his account on consecutive days and then withdrawn on consecutive days.

Meanwhile, Williams' family last night hit out at rumours that suggested the dead man was involved in risky sexual practices.

In a statement they said speculation linking the secret service employee to a male escort and bondage equipment had been "very distressing".

Williams, who was on secondment to MI6, was found dead in a bag in the bath of his government flat on Monday.

As police continued to investigate whether the GCHQ codes expert lived a secret double life, his family paid tribute to the murdered spy.

They said: "Gareth was a generous, loving son, brother, and friend, and he was a very private person.

"He was a great athlete, and loved cycling and music.

"His loss has devastated us and we would ask anyone with information to come forward and assist the police inquiry."

Williams was days from completing a one-year secondment to the Secret Intelligence Service, MI6, in London.