Vast crowds descended on central London Saturday demanding a second referendum on Britain's exit from the European Union.

The protesters began near Park Lane and worked their way down Whitehall, past Downing Street, before ending at Parliament Square. In a statement, the organizers of the march estimated that up to 1 million people attended. Authorities have not given estimates on crowd sizes.

Crowds march through central London holding European Union flags and anti-Brexit signs.
Crowds march through central London holding European Union flags and anti-Brexit signs.
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Pro-Brexit and anti-Brexit demonstrators argue at Parliament Square as lawmakers in the House of Commons debate nearby.
Pro-Brexit and anti-Brexit demonstrators argue at Parliament Square as lawmakers in the House of Commons debate nearby.
Henry Nicholls/Reuters
Anti-Brexit buttons rest on a table covered with an EU flag in central London.
Anti-Brexit buttons rest on a table covered with an EU flag in central London.
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An aerial view of the protesters in Parliament Square in London. There are no official numbers for the size of the turnout.
An aerial view of the protesters in Parliament Square in London. There are no official numbers for the size of the turnout.
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Actors Paul McGann and Patrick Stewart join other protesters demanding a second vote.
Actors Paul McGann and Patrick Stewart join other protesters demanding a second vote.
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Michela Beltracchi, an Italian who has lived in the UK for over 10 years, protests as part of the rally.
Michela Beltracchi, an Italian who has lived in the UK for over 10 years, protests as part of the rally.
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Protesters celebrate the passing of the Letwin amendment in the House of Commons.
Protesters celebrate the passing of the Letwin amendment in the House of Commons.
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A group of dogs dressed in European Union flag sweaters are seen at the anti-Brexit march in Parliament Square.
A group of dogs dressed in European Union flag sweaters are seen at the anti-Brexit march in Parliament Square.
Victoria Jones/AP
Mayor of London Sadiq Khan, who supports a second referendum, gives a media interview as demonstrators gather on Park Lane.
Mayor of London Sadiq Khan, who supports a second referendum, gives a media interview as demonstrators gather on Park Lane.
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