Meanwhile, Donald Trump is making policy on the hoof. It turns out that the Affordable Care Act of 2010, or Obamacare, is not so bad after all. A big section of his planned wall on the border with Mexico will be a fence. In the past presidents have usually arrived in the White House with a detailed set of policies. Mr Trump arrives with a tatty envelope scrawled with a few jottings on the back. Across the Atlantic, Brexit has opened a Pandora’s box: nobody knows whether Britain will leave the European single market or negotiate the equivalent of an associate membership. The Supreme Court has yet to determine how much say Parliament will have in shaping the negotiations