Here are some pictures Simon Perry posted of the event.

200,000 March Against Bush in London
By Naveed Raja for The Mirror.

A massive demonstration against George Bush drew up to 200,000 marchers on the streets of London today.
Organisers of the march, ending in a rally at Trafalgar Square, said the number was a record for any weekday protest in Britain.
With a huge police presence the Met reported no incidents of violence and the march passed off peacefully.
“This phenomenal response shows the depth of feeling of the British public towards this visit,” said a spokesman for the Stop The War Coalition.
The march started near Euston Station and went past the House of Commons and Whitehall before finishing at Trafalgar Square.
When the march passed Downing Street anti-war protesters booed and jeered at Bush and Blair inside number 10.
A huge papier mache statue of Bush was hauled down by protestors in Trafalgar Square in protest at the Iraq war.
Vietnam veteran Ron Kovic, on whose life the film Born on the Fourth of July was based, was the guest of honour.

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http://www.mirror.co.uk/news/allnews/content_objectid=13645118_method=full_siteid=50143_headline=-200-000-MARCH-AGAINST-BUSH-IN-LONDON-name_page.html
200,000 March Against Bush in London
By Naveed Raja
The Mirror
Thursday 20 November 2003
A massive demonstration against George Bush drew up to 200,000 marchers on the streets of London today.
Organisers of the march, ending in a rally at Trafalgar Square, said the number was a record for any weekday protest in Britain.
With a huge police presence the Met reported no incidents of violence and the march passed off peacefully.
“This phenomenal response shows the depth of feeling of the British public towards this visit,” said a spokesman for the Stop The War Coalition.
The march started near Euston Station and went past the House of Commons and Whitehall before finishing at Trafalgar Square.
When the march passed Downing Street anti-war protesters booed and jeered at Bush and Blair inside number 10.
A huge papier mache statue of Bush was hauled down by protestors in Trafalgar Square in protest at the Iraq war.
Vietnam veteran Ron Kovic, on whose life the film Born on the Fourth of July was based, was the guest of honour.
Other speakers at the rally included former leader of the SNP Alex Salmon and Labour MPs Jeremy Corbyn and Alice Mahon.
Former Labour MP George Galloway spoke to the crowd and described the march as “unbelievable”.
He said: “This is the largest march on a midweek day that this country has ever seen – it is absolutely overwhelming.
“We’re speaking for the majority of people in the world who want Bush out and who want Blair out.”
“Tony Blair added insult to injury by bringing this ignorant, foolish and dangerous man to these shores and I think we are speaking for the majority of the country.”
Caroline Lucas, of the Green Party told the crowd: “The eyes of the world are on Trafalgar Square today. We are making history.”