Campaigners packed Euston's Friends Meeting Hall on Saturday, 10 years after millions took to the streets to oppose the illegal invasion of Iraq.
The anger and determination was still palpable as hundreds reflected on a decade of struggle and planned for the future.
The so-called War on Terror, of which the invasion was a part, has since engulfed many more countries, most recently Mali.
But Labour MP and Stop the War Coalition (StWC) chairman Jeremy Corbyn set the tone, saying this was not a memorial event but "a way to mobilise forces" to ensure that Britain becomes a force for moral good and peace not war and violence.
He said that while the 2003 mass demonstrations had obviously not stopped the war all those who participated had been changed by it.
Commenting on the continuing slaughter in Afghanistan he said it was "the First World waging war on the people of one of the poorest nations on earth."
Author and activist Tariq Ali said that unfortunately StWC had been vindicated over all its warnings regarding the 2003 invasion and its repercussions.
These were not "accidental" wars and they were not necessarily going to stop.
"These are effectively imperialist wars backed by the US."
It pained him, he said, when "good people who opposed wars under Bush" became passive about those waged by Obama.
StWC was founded at Friends House in 2001 after the invasion of Afghanistan.
Convenor Lindsey German said in the 11 years since then they had made major achievements.
"We had millions of people come out time and time again campaigning to stop war."
This was a movement for hope and democracy. It was the politicians who subverted democracy and their decisions have had terrible consequences not just for the people of Iraq and elsewhere but for Britain too.
We have a government who can "find money for war and weapons but not for health, welfare and education.
"We were right in everything we said. They remain the same craven, warmongering liars as they were then."
Veteran left politician and peace campaigner Tony Benn received a standing ovation at the Stop the War Coalition conference in Euston on Saturday.
The StWC president expressed his pride at being asked to address the meeting and said: "We have built a peace movement so strong and powerful" that no government would be able to disregard it.
He said that empire had just been accepted in his childhood but that this was no longer the case with the US and its allies' attempts to dominate the world.
The "Islamic threat" justification was merely the same rhetoric used against communism during the cold war and must not be allowed to be used as an excuse for US domination, he said.
"It is interesting that our troops are not described as a Christian threat," he added to much laughter.
WAR will continue to rage across the Middle East and north Africa until the Israel-Palestinian conflict is resolved, Palestine's ambassador to Britain said on Saturday.
Manuel Hassassian told the Stop the War Coalition conference in London: "There is one constant factor destabilising the region - the non-solution of the Palestine-Israel problem."
Palestinians were dying day after day in their quest for self-determination, he added.
"When are the Western powers going to learn that they cannot put the victimiser and the victim on the same footing?"
He lambasted the hypocrisy of the West's portrayal of Israel as a "bastion of democracy."
He said: "Israel continues to build colonies, invading our land. Israel has a war agenda, not a peace agenda.
"It has been fooling the PLO for years by claiming it is negotiating while building more colonies, dividing the West Bank into three parts."
Mr Hassassian condemned US President Barack Obama, who had claimed that his first priority when elected had been to resolve the Israel-Palestine issue.
"The US is not an honest broker, third party. It is an interested party. The US considers Israel a strategic asset," he said.
He demanded that Israel move its "apartheid" wall which has encroached on Palestinian territory.
"Palestinians don't need your charity," he told he audience to huge applause, "we need an end to the occupation."
A delegation of West Bank firefighters received a rapturous response from the assembled activists.
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The Con-Dems have had it their way too long. We have to turn this country around