A police firearms officer left a gun in a coffee shop where it was discovered by a member of the public, Scotland Yard said today.
The pistol was reportedly left in the toilets of a central London branch of Starbucks by a police bodyguard who was once Tony Blair's close protection officer.
The Sun reports the gun, a semi-automatic Glock 17, was left on the floor of the cafe's only toilet for 20 minutes.
The newspaper says it belonged to a high-flying female officer in her 30s. She took off the belt holding the firearm when she used the toilet and then bought a coffee, forgetting she had left the gun behind.
The pistol was eventually linked to her when police compared its serial number to those logged at a police armoury.
A Scotland Yard spokesman said: "A police-issue firearm was left unattended in a central London cafe on 29 August and was found by a member of the public.
"The weapon belongs to a Metropolitan Police authorised firearms officer who was on duty at the time."
It is understood the gun was left in the coffee shop by mistake.
An investigation is being carried out by Scotland Yard's Directorate of Professional Standards.