Laughter, anger, slogans, chants - the day the marchers came to town

There was standing room only on the 9.59 from Oxford to London Paddington on Saturday morning – and precious little of that.

If the accessory of choice on the weekday First Great Western is the furled-up umbrella, on Saturday it was the furled-up banner. A man in a crumpled greatcoat inadvertently did rather a lot of damage with one that read 'Give Peace A Chance', tripping up a woman with dreadlocks.

Strangers cheerfully discussed their opposition to war on Iraq, or at least the need for a United Nations mandate. "There's just been another inspection", a man wearing a trilby told his friend. We all pricked up our ears. But he was talking about racing at Ascot, rather than weapons in Baghdad. He and his friend got off at Reading, muttering something about "bloody freedom fighters".

Those of us going on the Stop the War march had, on arrival at Paddington, to determine our strategy. Mine was to head for Piccadilly Circus, then walk up Shaftesbury Avenue to meet the route B marchers. They were led by the veteran dissident Tariq Ali and the actor Pete Postlethwaite, who wore a faintly bemused expression. He told me that he hadn't expected to be at the front, he'd just arrived early on a coach from Shropshire.

The latte-drinkers in All Bar One stared as the march passed through Cambridge Circus. A forest of placards and banners – some witty, some obscene, some genteel, such as the exhortation to 'Make Tea, Not War' – underlined the conviction that Tony Blair is way out on a limb.

'Regime Change Begins At Home' threatened one banner. 'War Is Terrorism With A Bigger Budget' thundered another. And, missing the point slightly, 'One Stockbroker Is One Too Many', carried by students from the London School of Economics. Maybe it was left over from the May Day protests, and they couldn't be bothered to change the slogan. After all, one demonstration is much the same as another. Except that this one wasn't. 'The West End Has Never Seen Anything Like It,' observed a notice outside the Queen's Theatre. It referred to a play, Contact, but more accurately summed up the scenario outside.

Along Piccadilly, the doorman of the Ritz Casino, Condor Little, watched a million people pass by. "It probably won't stop Tony and Georgie from pulling off this apocalyptic stunt of theirs, but I still think it's brilliant," he said.

Three building contractors working on nearby Malta House were less enthusiastic. "Pity they don't all speak out against Arab terrorists in this manner," sniffed one. He said he had no desire to join the protest.

Yet as with all coalitions, not least the UN itself, certain participants were uneasy about being allied with certain others.

There was, at times, a palpably stronger anti-Israel than anti-war flavour to the demonstration, which caused Elaine Nyman, of Hertfordshire, some discomfort. "I moved back in the march because there are some banners I don't want to be behind," said Mrs Nyman, who is Jewish. "Obviously I loathe [Ariel] Sharon, but so do many Israelis." A veteran demonstrator, Mrs Nyman mused that history doesn't always vindicate such an outpouring of conviction. "I marched against [President] Kennedy during the Cuban Missile Crisis, and later we found he had been influential in calming things down. Maybe that will prove true of Blair, but I don't think so."

It was a bitterly cold day, especially once the marchers arrived in Hyde Park, and had nowhere left to march. Perhaps that accounted for the vigorous applause which greeted a series of mostly underwhelming speeches by Mo Mowlam, Tony Benn and others. Jay Buck, at any rate, was unimpressed. 'They're just playing to the masses,' he complained. 'I haven't heard anything really inspiring.'

It was inspiration enough that more than a million people were prepared to take to the streets.