Police arrested a man for jumping the security fences around the Houses of Parliament on Monday.
He was detained just a few metres from the main entrance to the building at about 5.40pm on Monday.
The intruder was described as white and bald. He was wearing dark glasses, jeans, trainers and a camouflage jacket, the Mirror reported.
The incident is not being treated as a terror-related, Met police said.
A spokesman for the force said: "At approximately 5.40pm police arrested a man at the Palace of Westminster for trespassing. He remains in police custody."