Trade union activists at the traditional May Day march across the capital used this year's event to pay tribute to late RMT union leader Bob Crow and Labour MP Tony Benn.
TUC General Secretary Frances O'Grady said they would both be 'hugely missed'.
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The 20-year-old was found fatally wounded on Roth Walk, near Finsbury Park, north London at around 3am on Saturday, Scotland Yard said.
Police have arrested a man wanted in connection with a burglary at the home of pensioner Richard Osborn-Brooks.
The rally comes after it emerged that the Home Office destroyed thousands of landing cards documenting the arrival of windrush-era migrants