On the one hand, there was the sense of elation at the tide of humanity that swept through the streets of London to protest against the war. On Pall Mall, the two demonstrations converged as if it were the confluence of the Tigris and Euphrates.

There was a sense of shared endeavour, determination and some hope that surely this would make a difference. It did make a difference, but, as we know only too well, the war took place nevertheless.

So it's with some bitterness and a lot of anger that those of us in the anti-war movement remember how right we were five years ago. It's easy to lose sight of that now, now that the senior staff of the British Army, the Daily Telegraph letters page, and the most conservative of institutions nonchalantly describe the war and occupation as a disaster.

Five years ago, it was very different. I was treated as mad, bad or both by journalists - not from Murdoch's mucky stables but from the BBC, and the liberal press - for daring to say that there were no weapons of mass destruction in Iraq and that the Iraqis would fight us if we invaded, not wash our feet in rose water.

It would be an idea to force from them their reflections five years on. Some of them have slinked off to a new cynical argument - you marched, but you achieved nothing.

Well, one of the things we achieved, coupled with the resistance in Iraq, was to ensure that that this issue would shatter the imperial pretensions of Blair's government and would overshadow his entire career. That's made it far more difficult for Gordon Brown to follow George Bush into a new war on Iran, though that is exactly what is being considered.

We also created the conditions in which rage at what our government did - supported, it must be remembered, by the majority of MPs - could find expression through political channels. My victory in Bethnal Green and Bow in 2005 showed hundreds of thousands of young people, young Muslim people, that it was possible to change things politically.

Alas, that message has not reached all, and deep pools of alienation and bitterness have bred some very nasty beasts. But the anti-war movement - and issuing from it Respect - are playing a role in refashioning a radical force in British society which can offer an alternative to nihilism and violence.

The response by the Stop the War Coalition to the Lebanon war in 2006 showed its continuing salience and helped speed the war criminal Blair to an earlier exit than planned.

The movement continues to harry the government. And in the elections for the London Assembly on May 1, I and my comrades intend to inflict another election upset, spreading out from our east London fastness to the capital as a whole.