© Caty PriceThe man handcuffed to the Buckingham Palace railings
The unidentified man, believed to be in his 30s and dressed in a white t-shirt and black cap, locked his left wrist to the iron gate and was threatening to harm himself.
Police were forced to clear tourists away from the area on Thursday evening as officers tried to negotiate with the man to "bring the situation to a swift conclusion."
The Metropolitan Police said in a statement: "At around 17:23hrs a man approached the gates of Buckingham Palace and handcuffed himself to them.
"Officers in the area immediately approached the man, believed aged in his 30s, who began threatening to harm himself.
"London Ambulance Service are also on scene. Police are trying to speak to the man and bring the situation to a swift conclusion to ensure his safety and welfare."
No members of the Royal family are currently in residence at the palace as it is undergoing a major refurbishment programme not due to be completed until 2027.
Comment: See also: King Charles pelted with eggs by protester (November 2022)