Alexander Hitchens, of the Centre for Social Cohesion, said his group was invited to the debate with Mr Choudary on the understanding that it would be held on neutral ground with no segregation.

He said he was greeted by members of Al Muharjiroun on the door before being barred from entering.
'We were led to believe it would be completely neutral,' he said.

Outside the hall, Mr Choudary criticised British society as 'dirty' and predicted that, within one or two decades, Muslims would be the majority here.

Asked why he was living here, he said: 'We come here to civilise people, get them to come out of the darkness and injustice into the beauty of Islam.'