Around 500,000 people are expected to join an anti-war on Iraq march in London on Saturday, police predict.

Such a turnout would make it the largest peace protest in recent times and is expected bring the centre of the capital to a standstill. And organisers say the numbers could be higher still.

Metropolitan Police are advising people to stay away if they are not taking part in the rally.

If they are, the advice is dress for the weather and be patient.

Tony, don't go to war. You don't have the support of the people who elected you Stop the War coalition

"Large crowds move slowly. Please be prepared for a long wait before you set off and be patient with police," said Deputy Assistant Commissioner Andy Trotter.

"If we advise you to do something, there is a reason for it."

The Stop the War coalition which is co-ordinating the rally hopes the size of the demonstration - which members predict could top one million - will send a message to the prime minister.

"This is a chance for people to show what they really think about this war," said spokesman Andrew Burgin.

"They will be saying: 'Tony, don't go to war. You don't have the support of the people who elected you'."

	:	Anti-war protest
March routes and rally details

The 3.5-mile march will start from two positions at noon: Embankment, proceeding down Whitehall, past Parliament, and Gower Street.

They will converge at Piccadilly Circus.

The model Kate Moss and British designer Alexander McQueen will be leading a protest group from the fashion world.

Police advice to marchers

Be patient Wear warm clothes Bring snacks Carry a radio and monitor events on local radio

The march, which has been organised by Stop the War Coalition, the Campaign for Nuclear Disarmament and the Muslim Association of Britain, will culminate in a rally at Hyde Park where a succession of speakers, including former US presidential candidate Reverend Jesse Jackson, will take to a stage near Speakers' Corner.

Among other high-profile supporters expected to attend are the capital's mayor Ken Livingstone, human rights campaigner Bianca Jagger, former MP Tony Benn, the ex-president of Algeria, Ahmed Ben Bella, Labour backbenchers George Galloway and Jeremy Corbyn, and Liberal Democrat leader Charles Kennedy.

The crowd will be entertained by music from former Blur frontman Damon Albarn and the singer Ms Dynamite.

Glasgow rally

The prime minister's office said in a statement that he "respected the views" of those taking part in the march but suggested the gesture would make little difference to government policy.

"The way to prevent any military conflict is for Saddam Hussein to co-operate and fulfil his obligations as set out by the whole of the international community as embodied by the United Nations," said Tony Blair's official spokesman.

All police leave in the capital has been cancelled and 3,500 officers drafted in from the Met, the City of London force and British Transport Police to control the event.

Roads around the route will be closed to traffic from 1030 GMT until the rally finishes at around 1700.

The London march is one of many being held in cities around the world.

In Glasgow, protesters will start their rally early to coincide with Tony Blair's speech to the Labour Party spring conference in the city.

In London on Friday, five anti-war demonstrators chained themselves to a pink heart outside the gates of Downing Street.