My friend Tim Leunig is a cerebral thinker of the best kind. Though not party-political, he has worked for Tory chancellors and would give the same advice to governments of any stripe. Wikipedia calls him a prize-winning economist and that’s right, but he has a gadfly instinct and a remorselessly rational intellect that takes him into the deeps: into first principles, logical consequences and the reductiones ad absurdum of some of our trains of argument.