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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Police are investigating whether a Land Rover Defender found burnt out in West Horsley was involved in Tuesday night's ram raid.
The work, called Gift Horse, replaces the giant blue cockerel that previously sat on the plinth.
50 of the country's worst pollution blackspots are in the capital. Many in places you may visit every day.