(FILES) A pro-remain protester holds up an EU flag with one of the stars symbolically cut out in front of the Houses of Parliament shortly after British Prime Minister Theresa May announced to the House of Commons that Article 50 had been triggered in London on March 29, 2017. June 23, 2026 marks 10 years since the UK voted for Brexit, upending the country's politics and triggering fraught negotiations that finally concluded when it left the European Union in January 2020. Immigration, trade and the economy were all key issues during the Brexit campaign. (Photo by OLI SCARFF / AFP via Getty Images)