The police were out in force as thousands of students marched through central London.
Some 4,000 officers were on duty, as demonstrators marched peacefully in a protest against higher tuition fees and “privatisation” in universities.
After the violence of last year’s major fees protest, the police had warned they might use plastic bullets in “extreme circumstances”.
Police said 24 people were arrested, mostly for breaches of the peace.
Police estimate there were about 2,000 protesters, but organisers put the number attending at 15,000.
Scotland Yard said three arrests were for public order offences, one was for possession of an offensive weapon, three were for going equipped and 12 breaches of the peace.
At lunchtime, some protesters broke away from the march and set up tents in Trafalgar Square, but were eventually moved on.
The crowd marched to the City of London, where a protest against corporate greed has been taking place outside St Paul’s Cathedral.
BBC correspondent Mike Sergeant was with the protesters as they neared St Paul’s and the City.
“The march is moving slowly, sedately even. It is quite extraordinary the way it’s being policed,” he said.
“It’s the most tightly controlled march through London that I have ever seen. Very little opportunity for protesters to break away – an enormous contrast to last year.”
The student protest, organised by the National Campaign Against Fees and Cuts, is against the government’s plans for a market-driven higher education system and the rising tuition fees.
“We are being told by a cabinet of millionaires that we will have to pay triple tuition fees,” said campaign leader Michael Chessum.