Years ago, when sculptor Ann Carrington’s young son had chickenpox and couldn’t go to nursery, Carrington took him roaming in London. At one point they stopped near Trafalgar Square, captivated by the window of a stamp shop. They couldn’t go inside, but Carrington’s eye was caught by a tiny stamp with a profile of The Queen, designed by Arnold Machin in 1970; she went back the next day and bought it. ‘I knew it was the beginning of something,’ she says. ‘When I blew
