Thousands of workers marched through the centre of the capital for a rally to mark May Day.
A series of speakers denounced Government cuts and called for a fightback against them.
Organisers put numbers for the event at 10,000. Scotland Yard did not give a figure but said the event was peaceful with no reported problems.
A few people chanted "Topshop Topshop - Pay your taxes" as they passed a branch of the store in The Strand, following controversy over the tax affairs of boss Sir Philip Green, but three police officers standing outside plus security staff inside were not called upon to intervene and the shop remained open.
The event, put on by trade unions and international organisations, had as its core demands trade union rights, human rights and international solidarity, and was designed as another stage in the fight against cuts and job losses following the mass turnout in London on March 26.
Veteran left winger Tony Benn told the crowd: "We are about solidarity. It is important to remember that the real conflict in the world is between the majority who create the world's wealth, and the handful who control the world's wealth."
He added: "All the gains that have been made have been made by people like ourselves, campaigning year in and year out.
"This week, local authorities have got their elections. We must use our vote to build on what the TUC did on March 26, and work for a better society for ourselves and our children and grandchildren."
Sarah Veale of the TUC said that cuts in public spending would have a devastating effect on services. She added: "It's going to have a particularly devastating effect on women, both as the providers and main users of services.
"It's given new meaning to the phrase 'women and children first', because that's where the cuts are going to bite."
