Thousands of campaigners have gathered in London for a three-day forum against war, racism and corporate power.
One of the themes of the forum is the situation in Iraq
The European Social Forum will include seminars and musical events and will culminate in an anti-war march.
Tim Lezard, 34, from Gloucestershire, was involved in organising the forum and chaired one of its opening seminars.
He writes about his experience for BBC News Online.
At last it's here. After months of planning, the European Social Forum has finally arrived on the streets of London.
It's been going less than 24 hours but there's already an unmistakable buzz in the city as delegates wearing different-coloured wrist bands wander round the capital poring over their 76-page programme, handing out leaflets and pasting stickers on everything that doesn't move.
This is a huge event, with around 20,000 people from all over Europe and beyond coming together to engage in debate, organise action and build networks within the social justice movement.
We're always being told young people have no interest in politics.
Well, this event rebuts that emphatically.
The people here are interested in politics all right, they're just not interested in politicians and governments that ignore their views.
They feel let down by a political system they feel neither represents them nor their beliefs, and they're gathering in London to find their voice.
There's plenty of guidance for them, with a huge variety of international speakers appearing at seminars at Alexandra Palace and at various locations throughout central London.
Ally Pally, which has its own ESF bus service from Turnpike Lane tube, is a wonder of colour and energy.
Thousands of delegates decorated with T-shirts and badges showing off their political allegiances, walk round chatting to complete strangers like they've known them all their lives.
"We prefer to see people's similarities rather than pick on their differences," explained a young Hungarian woman.
I chaired a plenary on the war at which Tony Benn was speaking.
Tony Benn was one of the speakers on the first day of the forum
With people unable to understand English receiving simultaneous translations through headsets, Benn finished his speech with a rallying call:
"If we don't work to change the world, then there is no hope for us. But if we do work together then there is no power in the world that can stop us."
Benn was joined on the platform by a German MEP, an Italian peace worker, a Turkish human rights lawyer and an Irish journalist, and to me this summed up the beauty of the ESF: its inclusivity and diversity.
It is everything the establishment is not. At a time when world leaders have been forced to conspire in ever-more isolated spots, the ESF is unashamedly vibrant and on the streets, connecting with people.