POLICE condemned "irresponsible" drunkenness after arresting 21 people when violence broke out at an unauthorised Glasgow park rave to coincide with the royal wedding.

One officer was taken to hospital with a head injury after police moved in to break up the unofficial party in Kelvingrove Park, and police say more arrests could be made as they study video footage.

More than 4000 revellers, mostly in their teens and early-twenties, converged on the beauty spot yesterday and the majority were drinking.

But as officers praised crowds in London, where there were just 55 arrests among the million that lined the streets for the royal wedding, Strathclyde Police were forced to step in to break up the unauthorised park party, apprehending revellers for disorderly behaviour and drunkenness.

Youths were seen with blood running down their faces after sporadic fights broke out around the park, and there were reports of police cars being damaged. One van was seen to have its windows smashed.

As youths began to depart last night, they left much of the park carpeted with beer bottles, cans and carrier bags.

One local resident said it was “shameful” that youths had “trashed the park” and said it had been left in a worse state than if it had been used for an organised three-day rock festival.

Police said the officer who was injured had been discharged from hospital following treatment and was expected to make a full recovery.

Chief Superintendent Bernard Higgins said: “It’s really disappointing that on the day of the royal wedding we witnessed the scenes we did.

“We made a number of arrests at the time and we will now study CCTV footage and make further arrests if appropriate.

“The level of drunkenness was completely unacceptable and frankly irresponsible.”

Glasgow City Council, which now has to mount a huge clean- up operation, had warned against the unofficial party and urged people to find a “safer alternative” way to celebrate.

JJ Gardner, 19, one of two students who organised the event, spreading the word through social networking sites, said: “David Cameron said people wanting to organise street parties should forget the red tape.

“That’s what we’re doing.”

Meanwhile, republicans gathered outside the Queen’s official residence in Edinburgh to protest against the monarchy.

The group of more than 100 chanted slogans at the gates of the Palace of Holyroodhouse.

Protesters walked to the foot of the Royal Mile, briefly holding up traffic and open-topped tourist buses between the palace and the Scottish Parliament.

Scotland Yard praised the British public for helping make the biggest security operation in a generation in London for the royal wedding an “amazing success”.

Assistant Commissioner Lynne Owens said her 5000 officers should be “immensely proud” of their role in the “happy and safe” event.

An unprecedented covert and overt operation at the royal wedding resulted in the 55 arrests as well-wishers flooded central London’s streets.