In the run-up to the Scottish referendum of 2014 I was sitting in the House of Commons café area at Portcullis House, chatting to a friend from the BBC in Scotland and generally minding my own business. We were discussing some aspect of David Cameron’s premiership when my colleague told me to look up. I could, he said, ask the man himself. Cameron strode over, breaking out of the little procession of power, leaving advisers and bag carriers in his wake, to make a point about the campaign to keep Scotland in the United Kingdom.

Among pro-Union commentators and journalists there had been, said Cameron, a lot of stuff which suggested that he was lax and devoting insufficient attention to winning the vote triggered by his decision to accede to Nationalist demands for a referendum that autumn. Unionists needed to be assured – he said – that in 2014 for him, as PM, there was no higher priority than keeping Scotland as part of the UK.