Sebastiano and his mentor Michelangelo arrive in London

The exhibition Michelangelo and Sebastiano, which opens this month at the National Gallery, is a study of an asymmetrical relationship. Of the nearly 70 works included, Sebastiano will be represented much more fully: 21 paintings, 16 drawings and six letters to only two paintings, 15 drawings, four letters and three sculptures by Michelangelo. (Three works by other artists are also included.) But the salient feature of the exhibition is the fact that Michelangelo is by far the visually stronger