Scotland Yard is investigating after former prime minister David Cameron's bodyguard reportedly left his gun in an aeroplane toilet.
The weapon was found by a passenger, who handed it to flight attendants on a transatlantic flight, according to the Daily Mail.
The gun, believed to be a 9mm Glock 17 pistol, is said to have been left by a close-protection officer who took off his holster while using the toilet.
In a statement, the Metropolitan Police said: "We are aware of the incident on a flight into the UK on February 3 and the officer involved has since been removed from operational duties.
"We are taking this matter extremely seriously and an internal investigation is taking place."
Cameron, as a former prime minister, is entitled to continued security provided by the Met's Specialist Protection unit.
