A sales assistant was held at knifepoint during a raid on a London Colney betting shop.
A large sum was stolen during the robbery, which took place at around 5.45pm on Saturday.
The suspect went into the shop and showed a member of staff a knife before demanding they hand over the money.
He is described as between 30 and 40 years old, of medium build, with short brown hair, wearing a blacked hooded puffer jacket with the hood up, a white t-shirt and blue trousers.
After taking the cash he left the shop in the direction of Kings Road.
No one was hurt during the incident.
Anyone with information should contact Herts Police on the non-emergency number 101.
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