A Metropolitan Police officer has been arrested as part of an investigation into the discovery of ammunition - believed to be from the Met's own supplies - in personal lockers in the grounds of Buckingham Palace.

The investigation, by the Directorate of Professional Standards, commenced a few weeks ago following the reporting by officers from Royalty Protection of ammunition found in their personal lockers or belongings. The officer arrested is from the unit responsible for protecting the Royal Household (SO14) and normally works in a protection role, although he is not assigned to guard any individual member of the Royal Family.

It follows the announcement last week by Assistant Commissioner Mark Rowley that the Metropolitan Police was reorganising its Protection Command to improve operational efficiency. Mr Rowley said that this change had revealed a few pockets of poor behaviour which would not be tolerated. Nothing below the highest standards of personal behaviour is acceptable.

The arrested officer is being questioned on suspicion of misconduct in public office and unlawful possession of ammunition. He is in custody at a London police station and will be suspended from duty.

Investigators have been searching the officer's home address and the police building where the ammunition was found.

Established security procedures are unaffected by the investigation, which does not affect the daily work of the officers providing personal protection to the Royal Family. These units include some of the most highly trained and professional officers in the Met. They recognise the great responsibility their roles carry, and the privilege that goes with these positions.

Mr Rowley said last week that the Met is very proud of its protection teams and the work they have done in recent years, for example during the Golden Jubilee. But he made clear the determination to take decisive action where individuals may have behaved badly.

The Royal Household is aware of the on-going investigation and has been briefed on today's development. The IPCC have been informed.