Mark is clear that Brexit must be delivered.
He has delivered on his promise at the 2015 General Election to have a referendum on EU membership. As Government Chief Whip in the House of Commons, he ensured that the necessary legislation made it to the statute book, and gave us all a choice on our future membership of the EU.
While Mark backed Remain during the referendum campaign, he is clear that first and foremost he is a democrat, and now the people have spoken, we must fulfil that promise.
To that end, Mark voted for giving the Prime Minister the power to trigger Article 50, being one of the most vocal proponents for a simple, unamended Bill passing the Commons. Despite the efforts of Labour and the Lib Dems, he helped ensure that the Bill made it into law, and that Brexit was not blocked.
Mark wants Brexit to be delivered in a way that sticks to the promises made in the Conservative Manifesto at the 2017 General Election, which included leaving the Customs Union and creating no new barriers to doing business within the United Kingdom.
Regrettably, the Cabinet's Withdrawal Agreement put to the House of Commons on 15 January 2019 breaks these promises, which is why he could not support it.
You can watch Mark's full speech to the House of Commons explaining his decision at this link and read his full article in the Daily Telegraph at this link.