This morning’s Observer column.

There’s a delicious moment in Alastair Beaton’s satirical film, The Trial of Tony Blair, in which the former prime minister is finally arrested for war crimes on a warrant from the international criminal court. One scene shows the standard police procedure as Blair is inducted by the desk sergeant in a London station. Towards the end of the rigmarole, the policeman moves to take a saliva swab from him.

Blair is aghast, asks him what he is doing and – after the policeman has explained that he’s taking a DNA sample – asks who brought in such a stupid law. “You did, sir,” is the response…