You can see it now. The head of MI5 is having his weekly meeting with the security minister. They are casually lamenting Donald Trump’s worrying closeness to Vladimir Putin and the threat that this poses to Britain. Suddenly, Sir Ken McCallum gets to his feet so sharply that his tea sloshes onto the table. “Good Lord, minister,” he exclaims, palming his forehead. “I think we’ve forgotten to proscribe Russia.”