A copper is under investigation over an allegation that he left his post guarding Windsor Castle to go fishing.

The officer was reportedly posted to guard the castle’s Shaw Farm Gate last week when he left for a spot of fishing in the Thames. But he was spotted by a superior officer who was checking the perimeter of the castle grounds in a vehicle.

A Scotland Yard spokesman declined to confirm or deny the identity of the officer but said that a probe into the alleged incident had been launched.

He said: “The Metropolitan Police is investigating the conduct of an officer on duty at Windsor Castle on August 17.

“We are not prepared to discuss the matter while the investigation is ongoing.”

Security at the castle has been under the spotlight since 2003 when self-styled comedy terrorist Aaron Barschak gatecrashed Prince William’s 21st birthday party.

It is not known whether or not the PC caught anything.