A man has been arrested at Buckingham Palace on suspicion of possessing a Taser.
Security staff detained the 38-year-old as he went through security scanners at the visitor entrance shortly before 12.45 BST.
He was arrested on suspicion of possessing a firearm, namely a Taser, and remains in custody.
The Met said the incident is not thought to be terror-related. The palace declined to comment.
Parts of the building, which is the monarch’s official residence, are open to the public for 10 weeks each summer.
The Queen is currently at Balmoral Castle in Scotland on her summer break.