Demonstrators take part in a protest aimed at showing London's solidarity with the European Union following the recent EU referendum, in Trafalgar Square, central London, Britain June 28, 2016.

European Union's chief Brexit negotiator Michel Barnier and European Council President Donald Tusk pose with the Brexit draft text in Brussels, Belgium, November 15, 2018.

Britain's Prime Minister Theresa May attends a news conference following an extraordinary EU leaders summit to finalise and formalise the Brexit agreement in Brussels, Belgium November 25, 2018. Reuters/Dylan Martinez

European Commission President Jean-Claude Juncker and Brexit campaigner and member of the European Parliament Nigel Farage gesture before the start of the plenary session on the EU budget, at the European Parliament in Brussels, Belgium, May 2, 2018.

Flags are arranged at the EU headquarters as Britain and the EU launch Brexit talks in Brussels, June 19, 2017.

Supporters of the Stronger In Campaign react as results of the EU referendum are announced at the Royal Festival Hall, in London, Britain June 24, 2016. REUTERS/Rob Stothard/Pool

The front page of daily newspaper Le Monde, with the headline, "United Kingdom Leaves Europe" is seen at their printing works following Britain's referendum results to leave the European Union, in Tremblay en France, near Paris, France, June 24, 2016.

Demonstrators take part in a protest aimed at showing London's solidarity with the European Union following the recent EU referendum, inTrafalgar Square, central London, Britain June 28, 2016.

People hold banners during a 'March for Europe' demonstration against Britain's decision to leave the European Union, in central London, Britain July 2, 2016. Britain voted to leave the European Union in the EU Brexit referendum.

Traders from BGC, a global brokerage company in London's Canary Wharf financial centre react as European stock markets open early June 24, 2016 after Britain voted to leave the European Union in the EU BREXIT referendum.

Nigel Farage passes a European Union flag as he rides a bus while campaigning against Britain's Prime Minister Theresa May's Chequers Brexit plan, in central London, Britain, September 20, 2018.

Britain's Prime Minister Theresa May arrives with Britain's Permanent Representative to the EU Tim Barrow at an extraordinary EU leaders summit to finalise and formalise the Brexit agreement in Brussels, Belgium November 25, 2018.

Britain's Prime Minister Theresa May reacts during a news conference at Downing Street in London, Britain November 15, 2018. Matt Dunham/Pool via Reuters TPX IMAGES OF THE DAY

Britain's outgoing Prime Minister, David Cameron, accompanied by his wife Samantha, daughters Nancy (C) and Florence and son Arthur, leaves number 10 Downing Street, on his last day in office as Prime Minister, in central London, Britain July 13, 2016.

Nigel Farage (front), the leader of the United Kingdom Independence Party (UKIP) reacts with supporters, following the result of the EU referendum, outside the Houses of Parliament in London, Britain June 24, 2016.

Demonstrators take part in a protest aimed at showing London's solidarity with the European Union following the recent EU referendum, inTrafalgar Square, central London, Britain June 28, 2016.

Demonstrators take part in a protest aimed at showing London's solidarity with the European Union following the recent EU referendum, inTrafalgar Square, central London, Britain June 28, 2016.

People hold banners during a 'March for Europe' demonstration against Britain's decision to leave the European Union, in central London, Britain July 2, 2016. Britain voted to leave the European Union in the EU Brexit referendum.

People hold banners during a 'March for Europe' demonstration against Britain's decision to leave the European Union, in central London, Britain July 2, 2016. Britain voted to leave the European Union in the EU Brexit referendum.

European Commission President Jean-Claude Juncker jokes with European Union's chief Brexit negotiator Guy Verhofstadt ahead of a debate on the Future of Europe at the European Parliament in Strasbourg, France, February 6, 2018.

A pedestrian shields himself with a British union flag umbrella as he passes a billboard with a Brexit related campaign slogan in Leicester Square, London, Britain, March 29, 2018.