Police said the man, believed to be in his 30s, approached the gates at around 5.23pm on Thursday.

A Metropolitan Police spokesperson said officers were trying to speak to him to "bring the situation to a swift conclusion to ensure his safety and welfare".

The London Ambulance Service was also called to the scene.

Video showed the man, who was wearing a cap and sunglasses, with his left hand attached to the gates as officers spoke to him from a distance.

In May, a man was also arrested after approaching the gates and allegedly throwing shotgun cartridges into the grounds.

He was later detained under the Mental Health Act.