From every direction they poured onto London's Embankment, from up and down the country, a magnificent surge of workers, their banners and placards, transforming London for a day.
Previously the governor of the Bank of England expressed surprise that there has not been greater anger against the cuts from those affected. Even some trade union leaders, the very organisers of the demonstration, had estimated that 'up to 100,000' would march.
But the number on the day was six or seven times that as the opposition to the government's cuts was made clear. This was a reflection of the rage that has been building up, not having found a national expression until 26 March.
Not only was it huge, but this was unquestionably the working class on the march.
Firefighters, nurses, teachers, civil servants, transport workers, carers, young people, and their families surged through the city.
Union t-shirts, bibs and flags made blocs of purple, of green, of blue, orange, yellow, red and white. They marched against job cuts, against library closures, for a future for young people, for decent pensions, against the whole spectrum of suffering that the Con-Dem government intends to rain down on us.
But marchers drew confidence from their sheer number and also knew that more has to be done to stem the flow of cuts. Only days before the march the budget had granted further tax breaks to the richest and spelt greater suffering for the most vulnerable, such as the cuts in the winter fuel allowance.
Vince Cable has made the government's position clear. "Certainly we're listening, and I talk regularly to the trade union movement. I think [it's] important we have a dialogue with them, but we're not going to change the basic economic strategy." But that's what they think! Leaders of two of Britain's biggest trade unions called for coordinated strike action to follow the demo.
They are absolutely correct: this demo must form the platform for an almighty and powerful campaign of action, of occupations of threatened services and, especially, of coordinated strike action, so the cuts can be defeated.