Armed robbers threatened staff at a betting shop before escaping with cash and a mobile phone.
The raid happened at Coral bookmaker's in High Street, Ruislip,at 9.20pm on Saturday.
Two men entered the shop when it was empty of customers and about to close.
One of the men pulled out what appeared to be a small handgun and a taser and demanded money.
They fled with a small amount of cash and a mobile phone belonging to one of the staff.
Nobody was injured and there have been no arrests.
* Call 020 8247 7949 or Crimestoppers on 0800 555 111 if you have any information.