Rugby is a rough sport... especially if you're 10 years old and up against the mayor of London.

During a street rugby match against school children in Tokyo, Boris Johnson accidentally knocked over a boy named Toki.

The floppy blond haired 51-year-old quickly helped the boy up and apologised.

Toki took it all in stride.

I was happy to play against Boris, he said. And some of the strongest men in Japan.

Although they failed to reach the quarter-finals, the Japanese team's performance in the Rugby World Cup tournament sent shockwaves around the sporting world.

Johnson is in Japan on a trip to bolster trade and cultural ties with Tokyo.