The issue of sovereignty has mysteriously disappeared from the debate over Brexit. Some business-focused commentators even like to assert that in a ‘global, interconnected world’, sovereignty is meaningless. But a court judgment, delivered earlier this month, perfectly illustrates what is at stake.

The case is about national security. Specifically, it is about the legality of techniques used to identify and disrupt people intent on unleashing terror: the kind of terror we have seen recently in Manchester, Westminster, Borough Market and Parsons Green.