A British tourist is in trouble after he stripped naked and took a dip in the moat surrounding Tokyo's Imperial Palace – one of Japan's most sacrosanct sites.

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The shaven-headed, portly visitor led police on a two-hour chase, scaling a wall next to the water and hurling rocks at officers as shocked onlookers snapped photos.

Watch footage of the man's antics

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The 40-year-old had been touring the sprawling palace in central Tokyo with a group of Spanish tourists, Fuji Television said, although police later said that the man was a British national living in Spain.

He reportedly threw his belongings out of his pockets, stripped naked and dived straight into the brownish waters after claiming his bag had fallen into the moat.

Police approached the man in a small rowboat and tried to throw him a float, but he began beating the water in a threatening way, before throwing stones at the officers, barely missing them.

Palace 'off limits' to public

After he climbed out of the moat, he took a nearby pole and – his pinkish body still completely uncovered – charged at police, who pushed him back into the water.

He was seized immediately as he got out of the water a second time.

“I'm lucky I don't have very good eyesight,” one elderly woman told Fuji Television. “I can't believe he did this here, but he probably didn't know the significance of this area.”

Most of the centuries-old Imperial Palace is strictly off-limits to the public except on the Emperor's birthday and New Year's Day when the imperial family waves to cheering crowds from the balcony.

Most Japanese people show respect for Emperor Akihito, whose father Hirohito was revered as a demigod until 1945.

Brit bares all for sacred moat swim