Police are outside Vince Cable’s Twickenham office today amid fears students may descend on the building to protest over tuition fees.

Officers are taking it in turn to guard the MP’s constituency office, in Lion Road, after fears students could target the building in protest at the coalition Government's plans to treble fees.

The move will allow universities to charge up to £9,000 a year from 2012.

At Teddington School about 40 pupils tried to leave lessons to join protests taking place in the capital today organised by the Education Activist Network and the National Campaign Against Fees and Cuts, along with local student union officers.

But headteacher Richards Weeks said almost all of the pupils had been stopped at the school gates and had now returned to classes.

He said: “I have a duty to keep all students in school.

“We got no information about the protests.

“If we had we could have planned something within the school.

“We could have done a petition or had people talking, which would have been more effective."

Chief Inspector Duncan Slade, of Richmond police, said the police operation at Dr Cable's office had been put in place to make sure people’s “right to protest is protected” as well as to protect members of the public who are not involved.

This afternoon it emerged Dr Cable, Business Secretary in the coalition Government, was on a trip to Moscow.