(FILES) In this file photo taken on March 25, 2017 an EU flag and a Union flag held by a demonstrator are seen with Elizabeth Tower (Big Ben) and the Houses of Parliament in London. - Four and a half years after Britain voted to leave the EU and as eight months of painstaking trade talks reach a climax, Boris Johnson is set on December 13, 2020, to answer the most fundamental question: what is Brexit? Britain left the EU in January and is in a standstill transition period until December 31 while both sides thrash out the terms of their new trading relationship. (Photo by Daniel LEAL-OLIVAS / AFP)
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