The Metropolitan Police Flying Squad is hunting a gang of armed robbers who raided a shop in the grounds of Windsor Castle.
The shop is in the public grounds of the Queen's Berkshire home
Staff were preparing to open the Windsor Royal Farm Shop at the Queen's Berkshire residence on Monday at 0700 GMT when three balaclava-clad men burst in and threatened them with a hand gun.
The men stole cash before fleeing in a silver BMW.
The shop is in the Queen's Home Park on Datchet Road, Old Windsor, and sells food from royal farms and gardens including apples and apple juice from Sandringham.
No-one was injured in the robbery and no shots were fired.
A Scotland Yard spokesman said: "The protected secure area of the castle and grounds were not breached."
In July, comedian Aaron Barschak breached security at Windsor Castle to gatecrash Prince William's 21st birthday party.