British royal Prince Harry ruined a friend's 21st birthday party by hurling smoke bombs into a marquee.

The prince was a guest of good friend Lucy Kent's extravagant celebration bash in Gloucestershire, England, when he became out of hand after drinking too much champagne. The joke bombs didn't cause any injury, but the commotion convinced organisers to end the party for health and safety reasons.

A friend of Kent's tells British newspaper Sunday Express, "She was really cross about it.

"The party was meant to be an all-nighter but after Harry released these toxic things at about one o'clock in the morning everybody had to get out.

"Until then everybody had been dancing but the disco had to stop - he ruined it for everyone."