London's deputy mayor has condemned those involved in yesterday's violence in central London as "fascist agitators" as he defended the actions of the Metropolitan Police.
Kit Malthouse said criticisms of alleged intelligence failings by the Met were "unfair" and added officers had carried out "a huge amount of work" in preparing for yesterday's massive TUC march.
Organisers estimated that between 400,000 and 500,000 people took part in a peaceful march through central London against the Government's spending cuts, which culminated in a rally in Hyde Park.
But separately there were violent clashes with the police in parts of the West End, and today more than 200 people are in custody.
Activists fought with riot police in Trafalgar Square, with some throwing missiles and attempting to damage the Olympic clock within the square.
A Metropolitan Police spokesman said officers had "come under sustained attack" as they tried to deal with the disorder and attempted criminal damage. The area was eventually cleared by around 2.45am.
But former Met deputy assistant commissioner Brian Paddick said there were not enough officers "in the right place at the right time" and suggested intelligence had not been heeded.
He told BBC Radio 4's The World this Weekend: "It appears to me that they just didn't have the right numbers of officers in the right place at the right time to prevent not only the problems at Fortnum and Mason but at Trafalgar Square. Again that was flagged up days before that they wanted to occupy Trafalgar Square.
"There was a lot more I think they could have done."
But Mr Malthouse, who chairs the Metropolitan Police Authority, dismissed criticisms by "armchair generals" and said the police had a "difficult balance" to strike, claiming anarchists were mingling with peaceful marchers.
He said many were a "nasty bunch of black-shirted thugs" who were intent on "rampaging" around the West End.
He told the programme: "We should all be angry that what was a peaceful and legitimate protest was hijacked by about 250 criminals, many of whom I am pleased to say have now been arrested, for violent insurrection means."
Asked about criticisms that there had been intelligence warning of trouble, he said: "I think that would be unfair. I realise in these situations that the armchair generals tend to come out but the truth is the police did a huge amount of work with businesses in the West End, and indeed preparing for the event.
"We put 4,500 police officers out there ... but it was a very, very fast-moving afternoon.
"I counted these anarchists myself. They were a nasty bunch of black-shirted thugs on Piccadilly and it was pretty obvious that they were intent on rampaging around and would be very difficult to control.
"In the end they were contained ... there is a difficult balance because they were intermingling with, and were in amongst, getting on for 400,000 TUC protesters.
"Without disrupting the march it would have been very difficult to isolate them and take them out. The truth is the police had to respond to when criminal damage was done and they did so."
He added: "We need to learn the lessons to make sure it doesn't happen again but also recognise that when you get a group of fascist agitators who want a fight there is not a lot you can do about it other than confront them."