Police fear an Australian tourist found battered to death in his hotel room may have been murdered in a case of mistaken identity.
Mr Thompson was in London during a six-week tour of Europe
Newton Thompson, 61, from Melbourne , Australia, was found dead in his London hotel room on 1 August.
It came only two days after the arrival in the UK of extradited convicted paedophile Robert Excell, who bore a strong resemblance to Mr Thompson.
Police believe a vigilante may have carried out the killing.
A Metropolitan Police spokeswoman said: "One line of inquiry is a case of mistaken identity. At this moment we don't have a motive for this murder."
Like Excell, Mr Thompson wore metal-rimmed glasses, and had white hair and a silver beard.
Excell, a British-born man who had served 37 of the past 39 years behind bars in Australia for offences against young boys, had landed at Heathrow Airport on 30 July amid much publicity.
Children's campaigners had expressed fears that Excell, who was forced to sign a sex-offenders' register when he landed, might re-offend in Britain.
Robert Excell, under a sheet, was accompanied by police at Heathrow
CCTV pictures showed Mr Thompson alive hours after the last reported sighting of him, by bar staff at the Comfort Inn in Paddington, west London.
The Australian tourist, a divorced father-of-two, was on a six-week tour of Europe.
His body was found by hotel staff. He had been severely beaten and his belongings stolen.
Det Ch Insp David Little said: "He was severely beaten. Noises of a disturbance were heard by other guests that night, there was some sort of fight and struggle."