Around 1,000 people crammed into the final rally of Marxism Festival in central London today, Sunday. There was a confident atmosphere and a mood to fight - alongside deep anger at the system.
The father of Edson Da Costa, who died in east London last month after being stopped by police, gave a moving speech to the rally.
"This is my first time speaking publicly," he said. "My name is Ginario Da Costa. I came to the UK 21 years ago with my boy, his nickname was Edson.
"I'm going to say thank you to everybody who has called me and said I need to come out and we need to get justice. I need you guys' support."
The audience gave him two standing ovations, and held a minute's silence for Edson and the victims of the Grenfell Tower fire.
Former Guantanamo Bay detainee Moazzam Begg said it "broke my heart" to hear Ginario speak. "It reminded me of my father who campaigned for me when I was stuck in Guantanamo," he said.
"He stood in front of audiences like this. Sometimes he found it hard to find the words but he spoke from the heart."
Moazzam said Edson's family had been "welcomed into a community" of people fighting back. He denounced the Tories for making people less safe - and the demonisation of Muslims.
"The most respected man of recent times was a convicted terrorist called Nelson Mandela," he said
"I'm all for radicalisation against racists and those who would destroy our basic rights."
Brid Smith, People Before Profit TD in Ireland, described a "level of deep bitterness and resentment in the Irish working class".
She celebrated the movements against the right in Britain, Ireland and the US.
She added that Jeremy Corbyn has given people hope for an alternative and that, "Revolutionary ideas must be inserted into those hopes."
Amy Leather from the SWP central committee stressed that the Tories have gone from "arrogance" to deep crisis within just a few weeks.
She hailed Corbyn's success in the general election and asked, "Who says now that Britain is a right wing country?"
Amy argued that the Grenfell Tower fire "sums up everything that is rotten, brutal and corrupt in Tory Britain'.
"This was corporate murder," she said to cheers.
Amy argued that Grenfell exposed the "reality of capitalism" and that we can't be divided in fighting the system.
"We want to destroy capitalism," she said. "We're fighting for a different world where things like racism, homophobia and oppression are things of the past."
Marxism saw meetings on everything from challenging Islamophobia to economic crisis, from the political crisis in Europe to Marxism and religion, from fake news to Marxism, nature and society.
Trade unionists, socialists, campaigners, Labour Party members and others discussed how to capitalise on the Tories' crisis and fight for a better world.
In a packed meeting on the Russian Revolution, Alex Callinicos from the Socialist Workers Party's central committee argued that the October revolution of 1917 had "universal significance".
He argued against those on the left who saw the revolution as irrelevant to today. He said that he admired Jeremy Corbyn, but that it was also important to say that Corbyn is a left reformist.
Alex said history has shown that left reformism "doesn't work" and argued that we "need a revolution" to get socialism.
In other meetings, speakers talked about the need to look at other places for lessons about social democratic parties, particularly Greece.
The Grenfell Tower fire came up in many meetings - and activists from other campaigns shared their experiences of fighting for justice.
Barrister Michael Mansfield addressed a meeting on Self-defence is no offence: from the Bradford 12 to the Rotherham 12.
He said the way "people have been marginalised, ignored and their voices not listened to" linked many justice campaigns.
Other meetings looked at the fight for justice over the Hillsborough disaster and the Battle of Orgreave. Sheila Coleman from the Hillsborough Justice Campaign stressed the importance for activists to keep control of campaigns.
Many of those at Marxism were there for the first time. Sadia joined the Socialist Workers Party at the event. "I really like the atmosphere here - it's been so welcoming. The best meetings I've been to were on Islamophobia and the roots of terrorism."
Other meetings discussed the fight against racism and the far right, and how to build a fightback over pay in the unions.
Activists went away energised for the fights ahead.