Men hold placards celebrating Britain leaving the EU on Brexit day in London, Britain January 31, 2020.

People wave the British Union Jack and England flags as they celebrate in Parliament Square on Brexit day in London, Britain January 31, 2020.

A pro-Brexit supporter smiles as he poses on Parliament Square, on Brexit day, in London, Britain January 31, 2020.

Anti-Brexit protesters hold banners outside the Scottish parlament, in Edinburgh, Scotland, Britain January 31, 2020.

A projection by the Mayor of London’s office displaying 'London - everyone welcome' is seen at Piccadilly Circus in London, Britain January 31, 2020.

Scotland's First Minister Nicola Sturgeon gestures as she delivers a speech, on Brexit day, in Edinburgh, Scotland, Britain January 31, 2020.

A man waves a British flag on Brexit day in London, Britain January 31, 2020.

People celebrate Britain leaving the EU on Brexit day in London, Britain January 31, 2020.

Anti-Brexit protester hugs a man while holding a placard on Brexit day in London, Britain January 31, 2020.

Anti-Brexit demonstrators visit Europe House to give flowers to the staff on Brexit day in London, Britain January 31, 2020.

Officials remove the British flag at European Union Council in Brussels, Belgium January 31, 2020. Olivier Hoslet/Pool via Reuters.

British pro-brexit Members of the European Parliament leave the EU Parliament for the last time in Brussels, Belgium January 31, 2020.

A man holds paintings as he walks up the stairs on Parliament Square, on Brexit day, in London, Britain January 31, 2020.

A pro-Brexit supporter holds a placard at Parliament Square on Brexit day, in London, Britain January 31, 2020.

People celebrate Britain leaving the EU on Brexit day at Parliament Square in London, Britain January 31, 2020.

A pro-Brexit supporter (L) and anti-Brexit demonstrator interact outside Europe House on Brexit day in London, Britain January 31, 2020.

People step on an European Union flag as they celebrate Britain leaving the EU on Brexit day at Parliament Square in London, Britain January 31, 2020.

A man poses for a picture on Parliament Square, on Brexit day, in London, Britain January 31, 2020.

A British bulldog toy and other souvenirs are pictured at a souvenir store, near Parliament Square, on Brexit day, in London, Britain January 31, 2020.

A countdown clock is illuminated at 10 Downing Street on Brexit day in London, Britain January 31, 2020.

British flags flutter near the Houses of Parliament, on Brexit day, in London, Britain January 31, 2020.

A person jumps over the European Union flag lying on the ground and covered with a mud on Brexit day in London, Britain January 31, 2020.

People celebrate in Parliament Square on Brexit day in London, Britain January 31, 2020.

A man burns an EU flag on Brexit day in London, Britain January 31, 2020.

People celebrate Britain leaving the EU on Brexit day in London, Britain January 31, 2020.

A man holds the dog on a leash with clothes on and a sign on Brexit day in London, Britain January 31, 2020.

A pro-EU demonstrator plays the guitar on Brexit day in central London, Britain January 31, 2020.

Anti-Brexit protesters hold banners outside the Scottish parlament, in Edinburgh, Scotland, Britain January 31, 2020.

Anti-Brexit protesters hold banners outside the Scottish parlament, in Edinburgh, Scotland, Britain January 31, 2020.

Newspapers and other souvenirs are pictured at a store, near Parliament Square, on Brexit day, in London, Britain January 31, 2020.

A man walks with a St. George's flag at Westminster bridge on Brexit day, in London, Britain January 31, 2020.

A general view shows the port on Brexit day, in Dover, Britain January 31, 2020.

A pro-Brexit supporter holds a placard at Parliament Square on Brexit day, in London, Britain January 31, 2020.

A dressed up person holds a flag on Parliament Square, on Brexit day, in London, Britain January 31, 2020. Image for illustrative purposes.

An official removes the European Union flag from Britain's Permanent Representation to the European Union in Brussels, Belgium January 31, 2020. Olivier Hoslet/Pool via Reuters

Britain's Prime Minister Boris Johnson visits The Industry Centre at University of Sunderland, on Brexit day, in Sunderland, Britain January 31, 2020.