The impersonator — Rory Bremner, Steve Coogan — speaks, in different voices, to a single primitive pleasure centre in his audience. Counterintuitively, we like the imposition of imposture. We connive at deceit, at replication, for the release of neurotransmitters, the flood of endorphins — the brandies of the brain. I once heard Peter Ustinov on a chat show replicate the sound of an electric bell being pressed.