Britain's most senior police officer has warned of more disorder on the streets after violent scenes marred the latest student protest over higher tuition fees.
The warning from Sir Paul Stephenson came as Downing Street indicated a crunch Commons vote on the proposals to raise fees will be held before Christmas.
Sir Paul said his officers failed to correctly assess the mood of protesters in a new political climate before the Millbank riot two weeks ago but the Metropolitan Police boss said they did not make that mistake on Wednesday.
The protests, which in London saw 35 people arrested and seven police officers injured, were described by veteran Labour MP David Winnick as "marvellous".
Scotland Yard deployed more than 800 officers, almost four times as many as on November 10.
Potential targets for occupation, including the headquarters of the Liberal Democrats, were encircled by officers as reserves surrounded Trafalgar Square.
Speaking about Wednesday's clashes, Sir Paul said: "The bottom line is we did not get it right two weeks ago and in my opinion we did get it right yesterday."
Sir Paul said out of the 35 arrested yesterday, nine were held for vandalising and looting a police carrier left stranded in the centre of Whitehall.
Sir Paul defended the decision to "kettle" thousands of protesters, including many school pupils, in Whitehall, close to the entrance to Downing Street.
He said when several large-scale marches linked up in Whitehall police wanted to stop them getting into Parliament Square and beyond.