“One of the most successful – if bizarre – cases of overpainting a great artist’s picture came to light earlier this week, when it was disclosed that a Rembrandt self-portrait had been hidden under layers of concealing paint for 300 years. An unnamed pupil changed the 28-year-old Rembrandt into a flamboyantly dressed Russian aristocrat in a red hat, earrings, long hair and dashing moustache. For the next three centuries it was regarded as a portrait by an anonymous minor Dutch artist.” These things happen more often than one thinks. How?