The Whitehall area of London was brought to a standstill for nearly three hours today as a naked man straddled a statue in front of hordes of onlookers.
He was seen in a variety of poses on the statue of Prince George, the Duke of Cambridge, at times balancing precariously on the Duke's head.
The man was coaxed down shortly before 3pm and put into the back of a police van.
He was detained under the British Mental Health Act, Scotland Yard said.
Officers were called at around midday to reports that someone had clambered on to the statue, and they believed he might have a knife.
A 100m stretch of Whitehall, which is near the heart of Westminster in central London, was cordoned off as emergency services tried to persuade him to come down.
The man was seen waving his arms around and was talking to crews on the ground as crowds of onlookers gathered at either end of the cordon.
Whitehall runs from Trafalgar Square and is where the British Ministry of Defence is situated.
David Lee, a civil servant who works nearby, said he had watched the naked man for more than an hour.
"We saw him dismount the horse, then he sort of disappeared for a bit, then I assume he went into the police van," Mr Lee said.
"It's amazing that someone can cause this much disruption. Perhaps the cold finally got to him, or the wind finally got to him."