A man has been arrested after attempting to scale the scaffolding around the Elizabeth Tower.
Police confirmed the man jumped a railing at the Carriage Gates entrance to Parliament before climbing the scaffolding in place for refurbishment work.
The man was arrested by officers for trespassing on a designated site at 12 noon.
Police are not treating the incident as terror-related and there were no weapons recovered.
A Metropolitan Police spokesman said: "Police have dealt with a man climbing on the scaffolding at the Palace of Westminster.
"Officers were called at 11.32am to reports of a man acting suspiciously near Carriage Gates, SW1.
"When officers located the man, he climbed over the fence and climbed the scaffolding to the roof of the palace.
"The man was arrested at 12pm for trespassing on a designated site."
The Carriage Gates entrance was breached on March 22 last year when terrorist Adrian Ajao, also known as Khalid Masood, rushed into the parliamentary estate after abandoning his car.
Ajao stabbed unarmed officer Pc Keith Palmer to death and was able to get 20 yards into the estate before being shot.