On the evening of Friday, June 10, police were called to a west London hospital after a man was admitted with head injuries.
At around 4.30pm. that evening, he was injured in the Whitton Avenue West area of Greenford.
He was critically ill in the hospital until his death on Sunday, June 12th.
While formal identification is awaited, the man is believed to be Grezgorz Fiuk, 47, of Greenford.
His family has been notified.
In due course, a post-mortem examination will be performed.
In connection with the investigation, three people have been arrested. One was later released on bail, one was released under investigation, and one was detained.
Officers are not looking for anyone else in connection with the incident because the parties are believed to know each other.
Anyone with information, including witnesses who have yet to speak with police, is asked to call 101, ref 8115/10jun.
If you want to remain completely anonymous, call the independent charity Crimestoppers at 0800 555 111.