6 September 2010 Last updated at 09:44 ET

Police appeal over death of MI6 worker Gareth Williams

As the BBC's Jon Brain explains, the police are hoping the footage may jog someone's memory

Police investigating the death of MI6 worker Gareth Williams have appealed for help in tracing two people seen entering his central London flat.

Mr Williams' naked body was found in a bag in the bathroom of his Pimlico home by police on 23 August.

Detectives want to speak to a man and a woman, both of Mediterranean appearance, who called at the 30-year-old's home in June or July.

CCTV images of Mr Williams, captured on 14 and 15 August, have been released.

Officers said Mr Williams, from Anglesey, was found unclothed, in a zipped and padlocked red North Face holdall, which was in an empty bath in the ensuite bathroom.

A Metropolitan Police spokesman said there had been no forced entry into the flat, adding: "We do not believe there is any property missing.

"There is no suggestion the items within the flat were specifically posed. No drugs, or indications of drug usage were recovered."

'Complex death'

A post-mortem examination proved inconclusive and toxicology tests found no trace of alcohol, routine or recreational drugs.

Det Ch Insp Jacqueline Sebire said: "This remains a complex unexplained death inquiry.

"I would appeal to anyone who may have seen, or had contact with Gareth in the period between 11th and 23rd August to come forward and speak with us."

Detectives have released CCTV images of the 30-year-old entering Holland Park Underground station at about 1500 BST on 14 August.

Since returning from a planned holiday in the US on 11 August, he went shopping "on a number of occasions" in the West End and Knightsbridge areas", police said.

He also went into Harrods on 15 August, after visiting a cash machine, and then, at about 1430 BST, he was seen on CCTV images in Hans Crescent, heading towards Sloane Street, near the Dolce and Gabbana store.