Thousands in anti-war march

The Stop The War Coalition said the demonstration struck a significant blow for "liberty and democracy" and claimed that the attempt to stop it going ahead had swelled the number of supporters.

Police said 2,000 people joined the march, but organisers said the figure was at least double that number, with students, trade unionists and peace activists taking part.

The march disrupted traffic outside Parliament just as the Prime Minister was due to arrive in the Commons to tell MPs about the latest phase of British troop withdrawal from Iraq.

Gordon Brown was seen being driven along adjoining roads to Whitehall to avoid being caught up in the demonstration.

Scores of police officers escorted the banner-waving, chanting protesters from Trafalgar Square to Parliament, past Downing Street.

Lindsey German, convener of the Stop The War Coalition, said the group had been told time and again by police in recent days that they could not go ahead with the march, and she claimed the authorities and MPs had underestimated the determination of the anti-war movement.

She said her message to the Government was: "You will never draw a line under this war until you bring all our troops home. "And we don't want the troops brought home just so they can be sent to Afghanistan or the Iranian border. We want a permanent break with George Bush's murderous, imperialistic policies."

Ms German also claimed that Britain is now seeing restrictions on civil liberties as a direct result of the war in Iraq.

Andrew Murray, chairman of the coalition, announced to the crowd that the police relented just 30 minutes before the rally was due to start, adding: "This is a tribute to this movement and to everyone who has campaigned to assert our right to hold this Government to account for the criminal policies it is following around the world."