(FILES) In this file photo taken on July 13, 2016 Samantha Cameron (L) stands with her husband, outgoing British prime minister David Cameron (R) as he waves after speaking outside 10 Downing Street in central London on July 13, 2016 on his way to Buckingham Palace to tender his resignation to Queen Elizabeth II. - Severing a truculent partnership stretching back five decades, Britain finally went its own way late Thursday four-and-a-half years after its shock referendum verdict in favour of divorcing the EU. Brexit became reality as Big Ben struck 11:00 pm (2300 GMT) in central London, just as most of the European mainland ushered in 2021 at midnight. (Photo by Geoff CADDICK / AFP)