A study of the head of a middle-aged man, turned in profile to the right, with a heavy frowning face and pursed lips. The hair and back of the head are only slightly indicated. This carefully observed drawing is a study for St Bartholomew who appears at the far left of Leonardo's painting of the Last Supper in Milan. While the face and neck of the model are drawn in detail, the back of the head is indicated with a few simple strokes. It may be a definitive drawing for Leonardo to consult while working, or even his ‘fair copy’ to preserve his invention for future reference. Melzi's number 23.

Leonardo’s greatest work to reach completion was the Last Supper, painted for Ludovico Sforza in the refectory of Santa Maria delle Grazie in Milan, after work on the Sforza horse had been suspended in 1494. This revolutionary exercise in the depiction of emotion shows the reaction of the Disciples to Christ’s announcement of his imminent betrayal. But Leonardo’s experimental technique combining oil, tempera and varnish was soon deteriorating (he seems never to have worked in fresco), and what we see now is a ghost of Leonardo’s intentions. Leonardo must have executed many drawings as he refined the composition, but only a handful survive.

Text adapted from Leonardo da Vinci: A life in drawing, London, 2018