Anti-Brexit demonstrators stand outside the Houses of Parliament in London, Britain January 9, 2019. REUTERS/Henry Nicholls

Anti-Brexit protesters wave flags and placards opposite the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Toby Melville

An anti-Brexit protester wears a hat with a sticker opposite the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Toby Melville

Anti-Brexit protesters block the road outside the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Kevin Coombs

An anti-Brexit demonstrator stands outside the Houses of Parliament in London, Britain January 9, 2019. REUTERS/Henry Nicholls

A woman takes a selfie with a demonstrator wearing a Trump mask during a pro-Brexit demonstration in central London, Britain, December 9, 2018. REUTERS/Dylan Martinez

An anti-Brexit protester holds balloons opposite the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Toby Melville

Anti-Brexit demonstrators hold placards outside the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Henry Nicholls

Men holding placards advocating a no-deal Brexit perform right handed salutes as they demonstrate opposite the Houses of Parliament in London, Britain, December 11, 2018. REUTERS/Simon Dawson

Anti-Brexit protesters are seen outside the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Phil Noble

Pro-Brexit supporters demonstrate in central London, Britain, December 9, 2018. REUTERS/Dylan Martinez

A British protester holds a sign ahead of a meeting between Sinn Fein leaders and European Union Chief Brexit Negotiator Michel Barnier at the E.U. Commission headquarters in Brussels, Belgium, January 9, 2019. REUTERS/Francois Lenoir

A van carrying large caricatures of politicians drives past pro and anti-Brexit demonstrators outside the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Peter Nicholls

A man in a Santa Claus costume holds an anti-Brexit placard and rings a bell outside the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Peter Nicholls

Anti-Brexit protesters are seen outside the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Phil Noble

Anti-Brexit demonstrators shout, opposite the Houses of Parliament, in Westminster, central London, Britain December 11, 2018. REUTERS/Henry Nicholls

A student from anti-Brexit protest group 'Our Future Our Choice' demonstrates outside Stormont parliament building in Belfast, Northern Ireland, December 7, 2018. REUTERS/Clodagh Kilcoyne

Pro-Brexit and anti-Brexit demonstrators face each other opposite, the Houses of Parliament, in Westminster, central London, Britain December 11, 2018. REUTERS/Henry Nicholls

A Trump supporter waves a flag amongst anti-Brexit demonstrators during a protest opposite the Houses of Parliament, London, Britain, December 4, 2018. REUTERS/Henry Nicholls

Pro-Brexit supporters demonstrate in central London, Britain, December 9, 2018. REUTERS/Dylan Martinez

Pro and anti-Brexit protesters argue opposite the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Toby Melville

A bus with a pro-Brexit message passes an anti-Brexit demonstrator outside the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Peter Nicholls

Pro-Brexit and anti-Brexit demonstrators shout at each other opposite the Houses of Parliament, in Westminster, central London, Britain December 11, 2018. REUTERS/Henry Nicholls

A pro-Brexit protester stands outside of the Houses of Parliament in London, Britain, January 10, 2019. REUTERS/Toby Melville

Pro-Brexit supporters burn an EU flag during a UKIP demonstration in central London, Britain, December 9, 2018. REUTERS/Dylan Martinez

A Brexit supporter carries an anti-EU bag in London, Britain, December 10, 2018. REUTERS/Phil Noble

Anti-Brexit protesters stand next to an illuminated sign outside the Houses of Parliament in London, Britain, December 10, 2018. REUTERS/Henry Nicholls

A Boris Johnson impersonator walks alongside Brexit supporting Conservative MP Jacob Rees-Mogg in Westminster, London, Britain, December 11, 2018. REUTERS/Henry Nicholls