A woman has been arrested after attempting to scale the front gates of Buckingham Palace, Scotland Yard said.
The woman, believed to be in her 30s, was held by officers outside the Queen's official London residence at around 5.40pm on Saturday.
A Metropolitan Police spokesman said the incident was not being treated as terror-related.
Video posted on social media showed a woman being physically restrained on the gilded fence outside the palace by two police officers in front of stunned tourists.
She was then led away, shouting, to a waiting police car.
A Metropolitan Police spokesman said: "The woman, believed to be in in her 30s, was quickly detained by officers before she gained access to the palace grounds.
"She was arrested on suspicion of trespass under Section 128 of the Serious Organised Crime and Police Act 2005, trespass on a designated site and is currently in custody at a central London police station.
"The incident is not being treated as terrorist-related."