epa05877070 Britain's UK Independence Party (UKIP) MEP Ray Finch (C) cuts a cake as UKIP members celebrate the official triggering of Article 50 of the Lisbon Treaty, dubbed 'Brexit', at the Old Hack Pub in front of the EU Commission in Brussels, Belgium, 29 March 2017. Others are not identified. The British ambassador to the EU, Sir Tim Barrow, earlier 0n n29 March handed over the official notice under Article 50 of the Lisbon Treaty to European Council President Donald Tusk as part of the process that starts the formal proceedings of the United Kingdom leaving the European Union. Britain's Prime Minister had signed the notice following the June 2016 referendum to vote on Britain staying or leaving the European Union. EPA/STEPHANIE LECOCQ