In a 17th-century castle called Belton House just outside of the town of Grantham in Lincolnshire, England, there’s a mysterious painting of a black man in profile. He’s wearing a straw hat, a torn white shirt, with his arms resting on his left leg. Seated in front of what looks to be a landscape painting, the model looks relaxed, perhaps even bored. At the bottom of the portrait, there is a signature that has long baffled art historians. “The original catalog record had transcribed the signature as B-E-R-T-H-E,” says Alice…
