Thousands of students have taken to the streets in a new protest against the hike in university tuition fees.
Four thousand police officers are on duty as demonstrators march to voice their anger over funding cuts and plans to triple the fees.
They have been authorised to use baton rounds if necessary amid fears the event could be hijacked by activists.
Organisers claim "antagonistic" police comments ahead of the protest have made it more likely that trouble will occur.
They predict up to 10,000 people could join the demonstration as students claim the Government has betrayed them.
It comes almost a year after a mass protest over tuition fees erupted into violence.
Demonstrators claimed police were trying to intimidate them by warning they could resort to rubber bullets.
Beth Atkinson, 27, said: "It is ludicrous. It is antagonistic, it is like they are egging on a fight, which is frankly embarrassing."
John Roberts, 25, added: "I have got friends who haven't come along because of the threat of rubber bullets."
Imperial College PhD student Sheridan Few, 24, said: "I think it makes it even more important - we shouldn't be intimidated."
Luke Denne, 22, who got caught up in the chaos last November, said it is crucial the event passes off peacefully so the important messages can get across.
"It's all about public relations," he said. "Watching people smashing things up on TV is simply going to make people think students are troublemakers. It's easy to dismiss them. We need the public on our side."
He said the biggest issue is still the hike in tuition fees and the statistics show that university applications from poorer students have fallen disproportionately.
"Students don't expect higher education to be free but £9,000 a year is going to put people off. So students do need to march again. They should keep demonstrating."
One of the youngest turning out is Callum Hurley, who is challenging the Government in the courts.
He was 16 when he joined his first march last December, angry that he could become one of the first students to be stung by £9,000 fees in 2012.
He says it is important to show solidarity in numbers but questions whether ministers take any notice.
This is why he is pursuing legal action, arguing his human rights are being breached by the increase.
"Thousands of people can show anger but the Government doesn't have to listen," he said.
"The course of action I am taking - if the judge says the rise in tuition fees is unlawful - they will have to listen."
However, the march is about more than fees, grants and education and the route reflects that.
It will take students to the City - the part of London synonymous with wealth and banking.
The move is designed to reflect the growing discord in Britain after a year of riots and economic turmoil.
Joana Ramiro, one of the coordinators of the 2010 demonstrations, said: "This time we are looking more to the future. There is a broader politicisation.
"People have seen public sector cuts, whole departments closed down, attacks on their parents' pensions, even their own pensions if they have now started working. Attacks on the NHS budget. The consciousness is much broader than last year."
Many of those taking part have been stirred by the protesters outside St Paul's Cathedral.
While the marchers will be kept away from the cathedral, activists from the camp are expected to join in.