Holland Park station Aug 14
They also issued closed circuit television footage of Williams, who returned to Britain from a holiday in the United States on August 11, on shopping trips in the West End and Knightsbridge areas of London a week before his body was found.
The mysterious circumstances surrounding Williams' death has prompted some experts to question whether he was targetted because of the nature of his work.
"In my own opinion, a murder of this kind bears all the hallmarks of a professional killing and not a rage attack," said Professor Anthony Glees, Director of the Centre for Security and Intelligence Studies at the University of Buckingham.
"It looks increasingly to me that a hostile intelligence service was responsible. To me this looks like a Russian job -- they have killed in London before -- but it could also be an Iranian one."
And Mr Williams, 31 - found murdered at his central London home - was known to meet men in the capital's gay mecca of Vauxhall Cross and Soho in the West End.
Officers broke into his £400,000 top-floor flat in Pimlico when he failed to contact colleagues. Investigators suspect Mr Williams might have known his killer as there was no sign of forced entry.
So, not married, no girl, lives in $800,000 posh apartment in a gay section, owned by a Russian named company and has just traveled to the US and is so...so...so...frekin'n important, that he goes missing for two or more weeks before his bosses get off their arses and go looking for him. Top flyte!
It looks increasingly to me that a hostile intelligence service was responsible. To me this looks like a Russian job -- they have killed in London before -- but it could also be an Iranian one."