The scale of the anti-immigration"Unite the Kingdom" demonstration in London on Saturday far exceeded police estimates, resulting in tense and at times violent clashes between protesters and police.

It was believed to be the largest nationalist event in decades, with participants arriving in London by train and bus for the demonstration, billed as a"free speech festival".

When Robinson took the stage, he said:"Britain has finally woken up." He claimed that British courts had ruled that the rights of undocumented migrants were superior to those of the local community, citing Epping Council's unsuccessful case against the Home Office.

Whitehall quickly filled up and was closed before the first speakers, leaving thousands stranded on Westminster Bridge and in Parliament Square. Packed tightly around three giant screens, the crowds became so dense as to be dangerous. People climbed onto bus shelters and portable toilets to get a better view of the stage.

The huge crowd led to clashes with police. Police said at least 25 people were arrested and 26 police officers were injured, including four seriously. Those arrested have been charged with various offences, including hooliganism, violent conduct, assault and damage to property. An investigation has been launched and police are working to identify those involved in the riots.