Thousands of anti-war protesters cheered last night as an effigy of US president George Bush was toppled in a huge demonstration against his controversial visit to the UK.

As Mr Bush was entertained in Buckingham Palace, a few hundred yards away in Trafalgar Square a papier mache statue was dragged to the ground, sending a stark message from people opposed to the war in Iraq.

Protesters from Sussex were among the hundreds of thousands who took to the streets of London yesterday.

Many took the day off work to travel with fellow members of Sussex Action for Peace on a specially chartered coach to the capital.

The Stop The War Coalition (STWC) said up to 200,000 people from across the UK joined the protest, making it the biggest weekday demonstration ever held in this country.

Schoolchildren, students, pensioners and workers were still joining the start of the march near Euston Station more than three hours after it set off.

Marchers carried banners accusing President Bush of being a war criminal, while others blew whistles and horns, chanted anti-war slogans or wore unflattering masks of the Prime Minister or the President.

Scotland Yard estimated the number on the march to be 70,000, although this was hotly disputed by the organisers.

The number of arrests over the past two days grew to 50 by last night, with offences ranging from criminal damage to theft.

The effigy, which portrayed the President holding a missile and with Tony Blair in his pocket, was paraded at the head of the march before being erected in Trafalgar Square.

A group of protesters pulled down the statue in an echo of the toppling of a statue of Saddam Hussein in Baghdad towards the end of the original bombing campaign.

The President was kept well away from the demonstrators, leaving 10 Downing Street with Tony Blair just minutes before the marchers walked down Whitehall.

The two men, accompanied by their wives, left Downing Street by a rear entrance and were driven to Buckingham Palace by a route which had been cleared of any protesters.

A STWC spokesman said: "We think it is very funny that the President scurried out of the back door as a massive demonstration was passing nearby."

Deputy Assistant Commissioner Andy Trotter said: "We've had a very good tempered march and there have been no particular problems."

A total of 5,123 officers policed the route and Mr Trotter said the force was still on high alert because of intelligence of a possible terrorist threat.

The force said it was aware of a number of groups of French and German activists, some of them anarchist groups, who had come over to the UK specifically "hell bent on trouble".

Caroline Lucas, of the Green Party, brought a huge cheer from the crowd as she announced the demonstration was the biggest held in London on a weekday.

She said the tragic bombing in Istanbul yesterday "shows us our world is anything but more secure today.

"Our Prime Minister is an ally of George Bush but the British people are not. The eyes of the world are on Trafalgar Square today. We are making history."

Extra security was laid on outside Downing Street as anti-war protesters booed and jeered, hurling insults and gestures at President Bush as he passed.

The noise of the crowd escalated as they approached Trafalgar Square and the police were on hand in droves while a helicopter flew overhead.

As the protesters arrived at Trafalgar Square, they were greeted with music and a carnival atmosphere.

A stage had been set up with the 40ft gold statue with its head covered with a white cloth, which had the words "Time For Peace" daubed in red paint.

Demonstrators dressed in white protective nuclear clothing posed for photographers with mock nuclear weapons.

An imam took to the stage at the front of Nelson's Column and sang in Arabic to the crowd. Muslim worshippers unfurled square mats praying in the direction of Mecca on the steps of Nelson's Column.

The thousands gathered cheered and clapped speakers on stage as they berated George Bush and Tony Blair over the invasion of Iraq.

Anas Altikriti, spokesman for the Muslim Association of Britain, told the crowd the night would be a celebration of belief around the world.

Just after 5.15pm the huge gold coloured statue of President Bush was pulled to the ground.

A rope was slung over one shoulder of the President as the crowd chanted and cheered.

To the cries of "Down With Bush", the statue, still holding a nuclear warhead, toppled to the ground.

Former Labour MP George Galloway described the march as "unbelievable".

He said: "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."

A STWC spokesman added: "This phenomenal response shows the depth of feeling of the British public towards this visit."

For the seasoned campaigners up from Sussex, the size of the crowd was not unexpected.

John Catt, 79, a retired builder from Withdean, Brighton, said: "The number of people here doesn't surprise me because of the hypocrisy of Britain and America. They supplied arms to Iraq in the first place. I am opposed to everything Blair and Bush stand for concerning international affairs."

His daughter, Linda Catt, 43, said: "America is pillaging developing countries like Iraq in order to better its own economy. What it is doing is illegal.

"I am a solicitor and believe in the rule of law so I am here to show my anger."

While most were content to just shout their protest, Sandie Edmondson, 31, of Kemp Town, Brighton, was flashing the anti-Bush message on her chest to as many cameras as she could see.

The manager of a homeless project in Eastbourne said: "I want to get my message across in the best way possible. We want love, not war.

"I know in countries like Iraq you cannot protest like this but there are other ways of giving people freedom than invasion. I think things like education are far more important than violence and aggression."

Jackie Chase, 46, a music teacher from Fiveways, Brighton, said: "We all believe we should not have gone to war with Iraq and Bush needs to apologise to the UN."

Mr Bush may not have seen the crowds for himself but most protesters were hoping that he, and the American public, would be able to see it on television.

However, they were also anxious to point out their demonstration was against the President and no slur on Americans themselves.

Mrs Chase's American husband Nathanial, 50, a lecturer at the University of Sussex, was one of many protesting against the leader of his own country.

He said: "I am here because George Bush is not the elected president of the US. Since September 11 he has been running a break-away government made up of a small faction of the far Right."

Mr Chase could detect no hint of ill feeling directed towards the American public during the protest.

He said: "These people are not anti-American but they do not like imperialists and the far Right. I'm not sure if the march will change anything but it is very important the people create their own opposition, especially for future years."

An egg-throwing protester delivered a parting shot at President Bush as the huge anti-war demonstration drew to a close, police said today.

Of the 77 arrests made, the latest was a man suspected of throwing an egg which just missed Mr Bush's cavalcade outside Buckingham Palace late last night.

A spokeswoman said: "A 27-year-old man from Surrey was arrested at about 11.20pm yesterday opposite Canada Gate near Buckingham Palace for public order offence, throwing an egg at the cavalcade. It missed."