By far the most jaw-dropping revelation so far to have emerged in the extracts from David Cameron’s memoirs was buried in his account of the build-up to the Brexit referendum. Recalling his efforts to persuade Boris Johnson to back Remain, the former prime minister noted that “Boris had become fixated on whether we could pass legislation that said UK law was ultimately supreme over EU law”. He duly dispatched Sir Oliver Letwin on a “nightmare round of shuttle diplomacy” between Mr Johnson and the government’s lawyers to see if a way could be found to address his concerns by domestic legislation.

“But those lawyers were determined to defend the purity of European law and kept watering down the wording.” According to Mr Cameron, this epitomised