Sajid Javid's off his head. As soon as the legal door is cracked open to divergence, checks have to be introduced to ensure that no such divergence is taking place. Friction, friction, friction.
"I promise I'm not doing something, even though I absolutely could" doesn't cut it in international trade circles. Not even if you look them straight in the eye.
It's different now, of course, because the law prohibits divergence and so there are real consequences for cheats.
