The man, in his 40s, was found dead at the scene after officers were called to “concerns” at the address in Stanley Road at 4pm on Tuesday.
Officers from the Metropolitan Police’s specialist crime unit have been informed as part of the investigation.
A woman, who it is believed was known to the man, has been arrested.
A Met spokesperson said: “We are working to identify the deceased and inform the next of kin. A post-mortem examination will be held in due course.
“A woman has been arrested and a crime scene is now in place. The man and woman were believed to have been known to each other.”