Detectives investigating a robbery at a petrol station in Bourne End, Hemel Hempstead, are appealing for witnesses and information.
The incident occurred at the Shell service station in Stoney Lane, shortly after 8pm on Monday, May 22.
Two men entered the store and looked around before approaching the cashier. One of the men then leaped over the counter and threatened the cashier with a knife while demanding he hand over cash and cigarettes.
As customers entered the store, they were threatened by the second man and police were called.
The two suspects made off in a white van with a quantity of cash and cigarettes.
The first suspect is described as a white man who was wearing a black beanie hat, a blue jacket and jeans, a red T-shirt with white lettering on the front and black gloves.
The second is described as a white man, with short dark brown hair. He was wearing a dark hooded jumper with writing on it and dark coloured trousers.
Detective constable Jane Swift, from the Dacorum Local Crime Unit, said: “Thankfully no one was hurt during the incident but the victim has understandably been left shaken by the ordeal.
“We are doing everything we can to trace the people responsible and have a number of leads we are currently exploring. However, I would also appeal to members of the public who may be able to assist with the investigation to please come forward.
“If you saw what happened, saw two people acting suspiciously, or saw a white van leaving the area, please get in touch straightaway.”
Anyone with information is asked to contact Dacorum Local Crime Unit via the non-emergency number 101, quoting crime reference D1/17/4153.
Alternatively, they can contact the independent crime-fighting charity Crimestoppers anonymously on 0800 555111 or through its anonymous online form at www.crimestoppers-uk.org.