GUN-yielding men threatened staff at a betting shop before making off with cash and a mobile phone.
The armed robery happened at Coral bookmakers in High Street, Ruislip, at 9.20pm on Saturday.
Two men entered the shop when it was empty of customers and about to shut.
One of the men pulled out what appeared to be a small hand gun and a taser and demanded money before the pair made off with a small amount of cash and a mobile phone belonging to one of the staff members.
There were no injuries or arrests and the incident is being investigated by the MPS Flying Squad.
Anyone with information should call 0208 247 7949 or Crimestoppers on 0800 555 111.