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 one-year-old Yorkshire Terrier was attacked and killed while being taken for a walk.
The lifeboat crew carried the pair into their boat and dropped them off back at Tower Bridge as people watched from the riverside.
The huge painting took two graffiti artists thousands of hours to complete in east London.