For Davidson, the job of a portraitist is to “quarry” beneath the facade someone presents to the world, rather than to render a photographic likeness in oils. “What’s really important to me is that I’m after the truth,” he says. “I don’t want to in any way invest the painting with a self-indulgent sense of who I think that person is. There has to be an honesty to it.” Which is how he came to capture Brad Pitt just after the exhausted actor had got off a transatlantic flight, looking nothing like a Hollywood star. Or the former US president looking uncharacteristically uncertain.