M is a dazzling book which I imagine will spawn as many imitators as Longitude. It fits into no known genre: it is written with all the bravura of a novel but is not fiction; it is based on fact, but the facts are too sparse or too questionable to constitute a full biography. No matter. What M does is to introduce a completely new way of looking at paintings in their historical context. Normally historical context means some huge overview (‘the origins of the Renaissance’, ‘the death of Mannerism’), but M evokes the day-by-day context of a painter’s working career.

The painter is Caravaggio – Robb calls him ‘M’ because his real name was Michelangelo Merisi or Marisi. Caravaggio was the name of the small town east of Milan where his family lived. He was born in 1571 and died in 1610. These are almost the only certain facts known