Thousands of activists are expected to attend a May Day rally today to pay tribute to the lives of rail union leader Bob Crow and veteran political campaigner Tony Benn.
The traditional May Day event in London, which celebrates workers' achievements, will honour the two men, who died within a few days of each other earlier this year.
Crow died last month aged just 52 after leading a tube strike that saw him clash with London Mayor Boris Johnson. Benn died aged 88 just three days later. He was an MP for 47 years and a colourful commentator and diarist.
Tony Lennon, chief steward of the London May Day Organising Committee, said: "This year's London May Day presents a huge opportunity for the trade unions and the community to both pay tribute to the massive contribution made by Bob Crow and Tony Benn to the fight for workers' rights, and to send out a clear message that the battle goes on."
Mick Cash, acting general secretary of the Rail, Maritime and Transport (RMT) union, said: "RMT branches and regions have been building for a massive turnout on May Day in London in memory of both Bob Crow and Tony Benn under the theme: Don't Mourn - Organise."
The Occupy movement, which is fighting benefit cuts, is expected to target payday loan companies during a demonstration at the end of the May Day rally.
Last year's May Day rally in London passed off relatively peacefully.
In Greece, there was a general strike by the country's two largest trade unions in protest against the tough austerity measures are severely disrupting public services, including hospitals and transport.
In Turkey last year, riot police clashed with thousands of May Day protesters in Istanbul firing water cannon and tear gas at crowds in Istanbul.