Thousands of students, watched by 4,000 police officers, marched through London Wednesday to protest increases in university tuition. The march was largely peaceful, The Guardian reported. Police arrested about 20 people. About 200 protesters put up about two dozen tents next to Nelson\'s Column in Trafalgar Square. While they vowed to squat there indefinitely, police rousted them about an hour later, The Daily Telegraph reported. Police said they arrested a dozen of the campers during that sweep. \"Freedoms are being eroded everywhere in this country,\" said a 24-year-old Hertfordshire man identified only as Ben. \"This is just another example of that.\" Marchers said they were unhappy with the tripling of top university tuition, cuts in programs that pay expenses for needy students and what one student, identified as Greg, called \"the general atmosphere of cuts.\" The 21-year-old told the Times he came down from St. Andrew\'s University in Scotland to participate. The huge police presence may have kept the numbers down, the newspaper said. Organizers predicted about 10,000 people but about 2,500 were on hand when the march started at noon in the Bloomsbury neighborhood. A big protest turned violent in December, when a car carrying Prince Charles and his wife Camilla, duchess of Cornwall, was surrounded by angry students who chanted \"off with their heads.\" Police blocked the way Wednesday as marchers tried to head to St. Paul\'s Cathedral, the Financial Times reported. Occupy the London Stock Exchange protesters have been camped outside the cathedral for weeks.