Anti-war marchers have taken to the streets in London and Glasgow to call for the return of all troops from Iraq.
Demonstrators marched from London's Hyde Park to a rally in Trafalgar Square
They also demanded that plans to replace the Trident nuclear missile system be scrapped.
Organisers from the Stop the War coalition said 60,000 people turned out in London's Trafalgar Square, but police put the figure at 10,000.
In Glasgow, around 2,000 demonstrators gathered in George Square for the Bin the Bomb anti-Trident rally.
Stop the War said there was a very good turnout and insisted it showed the depth of feeling among the public.
The demo, jointly organised with CND and the British Muslim Initiative, was also opposed to any military action against Iran.
Protesters waved "Don't attack Iran" banners and posters labelling US President George Bush a "terrorist".
And Ismail Patel, from the British Muslim Initiative, said the central message of many of the campaigners was the importance of "freedom for the Palestinian people".
Politicians, entertainers and military families were among those who spoke in Trafalgar Square.
On Wednesday, Tony Blair told MPs that some 1,600 British troops would return from Iraq within the next few months.
And he said there were hopes that 500 more would leave by late summer.
Lindsey German, from the Stop The War coalition, said: "Whether 2,000 troops come home this year or not, it is too little too late and we must intensify our call for all troops to be withdrawn now and for Britain to break the link with George Bush's foreign policy."
And she added: "We know that many people are coming to the view that the government is addicted to war."
Relatives of soldiers killed or serving in Iraq set up a camp outside Downing Street on Friday to coincide with the protest.
They handed in a letter to Mr Blair calling for all British troops to be withdrawn immediately and demanding a meeting with him.
Protesters in London wore orange jumpsuits like those of Guantanamo inmates
Rose Gentle, whose 19-year-old son Gordon, a Royal Highland Fusilier from Glasgow, was killed by a bomb in Basra in June 2004, was among those sleeping in a tent in Whitehall until Sunday morning.
In Glasgow, church leaders, union chiefs and politicians from every party addressed the marchers.
Demonstrators there were angry at plans set out by Mr Blair late last year to replace Trident, carried by submarines based on the Clyde at Faslane, at an estimated cost of up to £20 billion.
The prime minister said retention of the nuclear deterrent was "crucial" to national security.
The Right Rev Alan McDonald, moderator of the General Assembly of the Church of Scotland, was among the marchers.
He said: "For 25 years the General Assembly of the Church of Scotland has consistently argued that nuclear weapons are morally and theologically wrong and I have always strongly supported that decision."
And SNP leader Alex Salmond said: "The people of Scotland have shown their opposition to Trident time and again.
"Instead of wasting billions on a weapons system that cannot protect us from terrorism, people would rather see that money spent on schools, hospitals and fighting crime."