THE MOVING THUMB

THE painting has several pentimenti — an Italian word for visible traces of earlier painting under layers of oils.

The most crucial pentimenti are around the thumb on Christ’s right hand, with which he is making the traditional blessing sign of benediction.

These pentimenti show the artist painted the thumb in a different position before settling on the one you see today. Now, there are 20 copies of the Salvator Mundi. But all show the thumb in just one position — the same as in the painting sold this week.

This suggests our £341 million painting is the original, because it shows Leonardo trying out several versions of the thumb before choosing his favoured position.

The others show no sign of experimentation — merely of copying.