Police were called to a flat in Mount Street, W1 shortly before 4pm on Friday 8 March following reports of a man found collapsed.
Police and London Ambulance Service pronounced a 63-year-old man dead at the scene having suffered apparent head injuries.
Police are still awaiting formal identification but believe the man to be Roberto Charles Troyan - known as Robert - who lived at 101 Mount Street, W1.
DCI Tim Duffield from the Homicide and Serious Crime Command said:
"We are appealing for anyone who knew Robert to come forward.
He was a very well known character in Mayfair; whom friends describe as kind and extremely generous.
We would urge anyone who may have seen anything suspicious in and around Mount Street to contact the incident room on 020 8721 4054 or call Crimestoppers anonymously on 0800 555 111.
More top news
As people across London celebrate Christmas, Micah Community Church share their Christian beliefs of the special day.
Police are now investigating the 'unexplained' death of a 23 year old man from Erith who was found dead in June.
Most of the squatters who took over the former RBS HQ on Trafalgar Square to feed homeless people on Christmas day have been evicted.