Employees of an East Finchley bookmakers feared for their lives when two men entered the shop and threatened them with a gun.
The men then stole cash from the William Hill betting shop on Church Lane, during the incident last Wednesday at 9.25pm.
The suspects, one described as Asian, of medium build, with short black hair and wearing blue jeans, a grey hooded top and a white surgical mask, the other black, 6ft tall, of medium build, wearing a dark hooded top and carrying a small gun in a blue bag, then escaped the scene.
They managed to steal £580 in cash and an iPhone.
Although members of staff were left shaken by the robbery, no one was harmed.
Police were called to the scene and the area around the betting shop was cordoned off.
T.T. Rasan, who owns the Convenience Store opposite the betting shop, said this was not the first time the betting shop had been a victim of an attack and businesses in the area were living in fear of further incidents.
He said: "People are always coming in stealing things and making life difficult for us. About twice a year we have armed incidents. The police come an hour later and are unable to do anything. No one seems to care."
Police are now asking people who were in the area at the time and might have witnessed the incident to come forward and help identify the suspects.
Detective Constable James Mess of Finchley Flying Squad said: “We would like to arrest these men as quickly as possible.
"It may be you saw them getting into a vehicle or hanging around near the area earlier in the day. Any information you have, no matter how small, could be vital so please contact us."
Joe Crilly, a spokesman for William Hill said: “The incident happened late at night when members of staff were preparing to close for the night.
“It is an ongoing police investigation and we are assisting in every way possible.
“Additionally, the Association of British Bookmakers) offers a reward to anyone who can provide information that leads to an arrest.”
Anyone who has information about the incident should contact DC Mess on 0208 358 1751
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