FILE - In this Wednesday, Feb. 27, 2019 file photo, a supporter of Britain's departure from the European Union, at right, holds a placard up in front of supporters of remaining in the EU, including Stop Brexit Man, Steve Bray, with his foghorn, outside Parliament in London. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Matt Dunham, File)

FILE - In this June 24, 2016 file photo, Nigel Farage, the leader of the UK Independence Party, celebrates and poses for photographers as he leaves a "Leave.EU" organization party for the British European Union membership referendum in London. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Matt Dunham, File)

FILE - In this Thursday, June 23, 2016 file photo, the front page of the Sun newspaper reporting on the EU referendum on a news stand in Westminster, London. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Tim Ireland, File)

FILE - In this Wednesday, June 22, 2016 file photo, British Prime Minister David Cameron reacts as he travels on his campaign bus near Bristol, England. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (Geoff Caddick/Pool via AP, File)

FILE - In this Thursday, Jan. 30, 2020 file photo, a man unfurls a Union and EU flag outside the European Parliament in Brussels. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Virginia Mayo, File)

FILE - In this Wednesday, June 22, 2016 file photo, a worker on a lift adjusts the EU flags in front of EU headquarters in Brussels. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Virginia Mayo, File)

FILE - In this Thursday, March 31, 2016 file photo, a 'Leave' supporter holds a banner near the Electoral Commission, in London. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Kirsty Wigglesworth, File)

FILE - In this Wednesday, June 22, 2016 file photo, European Commission President Jean-Claude Juncker speaks during a media conference at EU headquarters in Brussels. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Virginia Mayo, File)

FILE - In this Wednesday, June 15, 2016 file photo, a "Leave" supporter holds a banner on Westminster Bridge during an EU referendum campaign stunt in which a flotilla of boats supporting "Leave" sailed up the River Thames outside the Houses of Parliament in London. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Matt Dunham, File)

FILE - In this Wednesday, June 22, 2016 file photo, Britain's Prime Minister David Cameron attends a Britain Stronger In Europe event while campaigning for people to vote to remain inside the EU, in Birmingham, England. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (Geoff Caddick/Pool via AP, File)

FILE - In this Friday, June 24, 2016 file photo, Vote Leave campaigner Boris Johnson arrives for a press conference at Vote Leave headquarters in London Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (Mary Turner/Pool via AP, File)

FILE- In this Thursday, March 31, 2016 file photo, Nigel Farage, leader of Britain's UKIP party walks past a 'Grassroots Out' advertising lorry outside the Electoral Commission, in London. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust.(AP Photo/Kirsty Wigglesworth, File)

FILE - In this Wednesday, June 22, 2016 file photo, London Mayor Sadiq Khan, right, makes an address flanked by the leader of Britain's opposition Labour Party Jeremy Corbyn during a European Referendum "Remain" rally in London. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Matt Dunham, FIle)

FILE - In this Thursday, June 23, 2016 file photo, Britain's Prime Minister David Cameron and his wife Samantha leave after casting their votes in the EU referendum at a polling station in London. Five years ago, Britons voted in a referendum that was meant to bring certainty to the U.K.’s fraught relationship with its European neigbors. Voters’ decision on June 23, 2016 was narrow but clear: By 52 percent to 48 percent, they chose to leave the European Union. It took over four years to actually make the break. The former partners are still bickering, like many divorced couples, over money and trust. (AP Photo/Tim Ireland, File)