‘I’m an amateur,’ Barry Humphries tells me. The Australian polymath uses the word in its older sense of ‘enthusiast’ rather than ‘bungler’ and he feels no need to point out the distinction. He’s in London to perform a three-week residency at the Barbican — Barry Humphries’ Weimar Cabaret — with his fellow Australian Melissa Madden Gray, who uses the stage name Meow Meow.