Portrait of the Doctor of the Elector of Brandenburg, Leonard Thurneysser zum Thurn of Basel

In 1569 a Basel goldsmith's son named Leonhard Thurneysser came through Antwerp, and the city's leading painter, Frans Floris, set down his face. Thurneysser was about 38, self-taught, with no university degree, and already living by alchemy and homemade remedies. The grand title the picture now carries, physician to the Elector of Brandenburg, was still ahead of him. Only around 1571 did Johann Georg of Brandenburg take him on, after he treated the elector's wife, giving him rooms in a former Franciscan friary in Berlin for a library, a printing press and a laboratory. The panel itself carries a second story. For a long time no one knew who the sitter was. It passed as a self-portrait by Anthonis Mor, then as another painter, then simply as an unknown man, until Paul Boerlin recognised Thurneysser in 1975 by matching the face to engraved portraits of him.