The incident occurred around 16:00hrs on October 31, 2021, when the suspect entered the bookmakers and approached the counter, demanding money and pointing a gun at staff.
The man is described as a black male between the ages of 35 and 40, with short dark hair that is slightly balding.
The suspect fled the store with a large sum of money.
There were no reported injuries, but London Ambulance Service treated one woman for shock.
Anyone who has not yet spoken to police or anyone with information is asked to call 101 or tweet @MetCC with the reference 5386/31OCT21.
To remain anonymous, call the independent charity Crimestoppers at 0800 555 111.