Julian Opie, a complicated man who makes deceptively simple works of art, is showing me around his Old Street studio. ‘This is Diane von Furstenberg,’ he says, pointing to a splendid likeness of the fashion designer, 10ft tall and sporting, of course, a wrap dress, picked out with pin-sharp detail; her face, however, is no more than a bubble. ‘And this is Felicia, she’s married to a banker,’ he continues. Felicia is also bubble-headed and clad in evening dress and jewels, standing beside a neoclassical column. Another wealthy woman,Ika, looks on blankly from across the studio, elegantly posed in her best clothes, her head a cryptic white circle. ‘It costs £25,000 to be my model for the day,’ he explains. Now my face also resembles a shocked white bubble. ‘And then you can buy whatever work comes out of that day for the usual price — about £45,000 for a work this size.’