'Are there any more coming, then?'

There have been dafter questions, but not many. At 1.10 yesterday afternoon, Mike Wiseman from Newcastle upon Tyne placed his accordion carefully on the ground below Hyde Park's gates and rubbed cold hands together. Two elderly women, hand in hand in furs, passed through, still humming the dying notes from his 'Give Peace A Chance'. They were, had he known it, early, part of a tiny crowd straggling into Hyde Park before the march proper.

Half a mile away, round the corner in Piccadilly, the ground shook. An ocean, a perfect storm of people. Banners, a bobbing cherry-blossom of banners, covered every inch back to the Circus - and for miles beyond, south to the river, north to Euston.

Ahead of the marchers lay one remaining silent half-mile. The unprecedented turnout had shocked the organisers, shocked the marchers. And there at the end before them, high on top of the Wellington Arch, the four obsidian stallions and their vicious conquering chariot, the very Spirit of War, were stilled, rearing back - caught, and held, in the bare branches and bright chill of Piccadilly, London, on Saturday 15 February 2003.

Are there any more coming? Yes, Mike. Yes, I think there are some more coming.

It was the biggest public demonstration ever held in Britain, surpassing every one of the organisers' wildest expectations and Tony Blair's worst fears, and it will be remembered for the bleak bitterness of the day and the colourful warmth of feeling in the extraordinary crowds. Organisers claimed that more than 1.5 million had turned out; even the police agreed to 750,000 and rising.

By three o'clock in the afternoon they were still streaming out of Tube stations to join the end of the two routes, from Gower Street in the north and Embankment by the river. 'Must be another march,' grumbled the taxi driver, then, trying in vain to negotiate Tottenham Court Road. No, I said; it's the same one, still going, and he turned his head in shock. 'Bloody Jesus! Well, good luck to them I say.' There were, of course, the usual suspects - CND, Socialist Workers' Party, the anarchists. But even they looked shocked at the number of their fellow marchers: it is safe to say they had never experienced such a mass of humanity.

There were nuns. Toddlers. Women barristers. The Eton George Orwell Society. Archaeologists Against War. Walthamstow Catholic Church, the Swaffham Women's Choir and Notts County Supporters Say Make Love Not War (And a Home Win against Bristol would be Nice). They won 2-0, by the way. One group of SWP stalwarts were joined, for the first march in any of their histories, by their mothers. There were country folk and lecturers, dentists and poulterers, a hairdresser from Cardiff and a poet from Cheltenham.

I called a friend at two o'clock, who was still making her ponderous way along the Embankment - 'It's not a march yet, more of record shuffle' - and she expressed delight at her first protest. 'You wouldn't believe it; there are girls here with good nails and really nice bags .'

Cheer upon cheer went up. There were cheers as marchers were given updates about turnout elsewhere in the world - 90,000 in Glasgow, two million on the streets of Rome. There was a glorious cheer, at Piccadilly Circus, when the twin ribbons met, just before one o'clock.

The mood was astonishingly friendly. 'Would you like a placard, sir?' Sir? The police laughed. One, stopping a marcher from going through a barricade in Trafalgar Square, told him it was a sterile area, only to be met with a hearty backslap. 'Sterile area? Where did that one come from.' 'I know,' shrugged the bobby. 'Bollocks language, isn't it?' And the talk was of politics, yes, but not just politics. There were not the detailed arguments we had had, even during the last peace march in November, over UN resolutions and future codicils. This march was not really about politics; it was about humanitarianism.

'I'm not political, not at all. I don't even watch the news,' said Alvina Desir, queuing on the Embankment for the start of the march at noon. 'I've never been on a march in my life and never had any intention. But something's happened recently, to me and so many friends - we just know there's something going wrong in this country. No one's being consulted, and it's starting to feel worrying - more worrying than the scaremongering we've been getting about the terrorist threat. I simply don't see how war can be the answer and I don't know anyone who does. And, apart from anything else, as a black woman in London, it feels dangerous to spread racial tension after all that's been done.'

A Cheshire fireman nearby said: 'They will take notice of a protest like this. Our MPs, and Blair himself , were voted in by ordinary people like those here today. Blair is clever enough not to ignore this.'

Linda Homan, sitting on bench at 9.30 in the morning, watching a bright and dancing Thames, had come down early from Cambridge and was wondering at that stage whether many would turn up. Palettes of placards lay strewn along the Embankment, waiting. A trolley was pushed past filled with flags and whistles; there were more police - then, way back then - than marchers. 'I've never felt strongly enough about anything before. But this is so different; I would have let myself down by not coming and I think this will be something to remember.'

For Linda, like so many along these streets, it was her first march. Twelve-year-old Charlotte Wright, who came up by train from Guildford, Surrey, on her own. 'My parents aren't very happy about this but I think it's important. Bombing people isn't the right way to sort a problem out.' Jenny Mould, 36, a teacher from Devon. 'I drove up last night. It took seven hours but it was definitely worth it; the Government should, it must, listen to the people, otherwise what's the point in democracy?'

Retired solicitor Thomas Elliot from Basildon, Essex, a virgin marcher at 73, said: 'I remember the war and the effect the bombing had on London. War should only be used when absolutely necessary.' Andrew Miller, 33, from New Zealand, whose feeling, echoed by all around, was that 'all the different groups that are marching today show the world that the West is not the enemy, that British people do not hate Islam and Arabs and the coming together of people is the greatest way forward.' Lesley Taylor, a constitutional law lecturer who's lived across here for 29 years, holding a forlorn placard reading 'American against the war.' Why only one? 'I don't know any other Americans here. In the Eighties here I saw a lot of anti-American resentment, and now it's back. I accept that the perception of George W. Bush has something to do with this, but still... these are the same people the thinking middle-classes, who were so shocked and honestly sympathetic after September 11: how can they turn so nasty so quickly?

'Because America is making your Prime Minister go against the huge majority of the British people. And that won't be forgiven. Look about you. That's what this is about; not fierce party politics but a simple feeling that democracy, British democracy, has been forgotten.'

Chris Wall, a Nottingham mother who had brought down eight children with her: 'They talk about it at school and that's a good thing. Children need to be aware of what's happening in the world. And this is, of course, a peaceful protest.' It remained so all day, despite the numbers; by five o'clock police were reporting only three arrests.

In Hyde Park itself, a long line of purple silk lay on the grass, facing Mecca, and Muslims took off their shoes to pray. Beside it, artist Nicola Green had set up her Laughing Booth, and was encouraging people in to, obviously, start laughing, on their own, and be recorded; it was, she says, the most disarming of all weapons. The sky above the nearby stage grew dark, and the park grew even more astonishingly full.

Charles Kennedy won loud applause for stating that 'The report from Hans Blix gives no moral case for war on Iraq'; George Galloway won both applause and laughter for suggesting a new slogan: 'Don't attack Chirac'. Mo Mowlam warned: 'We will lose this war. It will be the best recruiting campaign for terrorists that there could be. They will hate us even more.'

Will yesterday, astonishing yesterday, change anything? The facts are undeniable. Perception is all.

If you look more carefully, in fact, at the warlike Wellington statue, a new tale emerges. The driver of the chariot is a boy. The reins are slack. The horses are not rearing with anger, but pulling up in mid-charge. Behind, the fierce, all-powerful figure is not the Spirit of War but the angel of peace, carrying an olive branch.