In June 2016, the people of the United Kingdom voted to leave the European Union. As the EU's chief negotiator, for four years Michel Barnier had a seat at the table as the two sides thrashed out what 'Brexit' would really mean. The result would change Britain and Europe forever. During the 1600 days of complex and often acrimonious negotiations, Michel Barnier kept a secret diary. He recorded his private hopes and fears, and gave a blow-by-blow account as the negotiations oscillated between consensus and disagreement, transparency and lies. From Brussels to London, from Dublin to Nicosia, Michel Barnier's secret diary lifts the lid on what really happened behind the scenes of one of the most high-stakes negotiations in modern history. The result is a unique testimony from the ultimate insider on the hidden world of Brexit and those who made it happen.