A mass protest being staged today against cuts in public spending was set to be the biggest for years as more people than expected turned up to send an angry message to the Government.
The TUC had estimated that around 100,000 union activists and other campaigners would take part in today's demonstration in London, but it was clear that hundreds of thousands had made their way to the city.
Unofficial estimates said that at least 250,000 demonstrators were packing into central London before a march had even started.
Dave Prentis, general secretary of Unison, told the Press Association that the turnout was "absolutely enormous and showed the anger of ordinary working people at the Government's cuts".
As he waited to set off at the head of the march he added: "We always expected an enormous turnout because Unison alone has laid on 500 coaches and a number of special trains but the numbers are simply incredible.
"These are ordinary families and working people, many with their children to send a strong message to David Cameron to halt the damaging cuts which are leading to the loss of tens of thousands of jobs and the closure of services including libraries and care homes."
Demonstrators started arriving in London hours before the march was due to begin, turning the Embankment into a sea of colour with banners, balloons and entertainers filling the banks of the Thames.
Steel bands, choirs, performers and dancers practised at the head of the march as tens of thousands of people, many with their children in tow, blew horns and whistles waiting patiently to march through central London to Hyde Park.
A rally later will be addressed by Labour leader Ed Miliband who was putting the final touches to his speech just minutes before he was due to start speaking.
Shadow chancellor Ed Balls was heckled by some protesters when he turned up to speak to union leaders at the head of the march this morning.
He said Labour was determined to continue campaigning against the spending cuts and would create jobs and build houses if they got back into power.
But several people shouted out at him "what are you going to do for us Ed?"