Staff at a bookmakers were forced to empty the tills and safe after a moped rider pointed a gun at them.
The male robber stormed Ladbrokes in Manor Way, Borehamwood, just after 4.45pm on Wednesday.
He demanded staff hand over cash and they did, before he left the shop.
Once outside, he got onto a moped which was being ridden by a second person, and they raced off towards Elstree Way.
Thankfully, no one was injured in the raid.
Police have been carrying out extensive enquiries since the robbery and are appealing for witnesses.
Anyone who saw what happened at the bookmakers or saw a moped being ridden round at speed in Borehamwood around 4.45pm-5pm on Wednesday should contact police on 101 quoting reference 41/46802/19.
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