‘When we rotated it 90 degrees it was obvious’: mystery sketch is rare Michelangelo draft for Sistine Chapel

Image of man battling serpents is confirmed as preparation for renaissance artist's masterpiece

A 16th-century drawing of a nude man, seen from behind, has been identified as a study by Michelangelo for his monumental masterpiece, the ceiling fresco of the Sistine Chapel in the Vatican.

The red chalk drawing has been linked to one of the figures battling serpents on the Worship of the Brazen Serpent painting. It is thought to date from 1512, shortly before Michelangelo painted that final section of one of the world's most famous works of art, which he had started in 1508.