Bernard Berenson (1865–1959) and Kenneth Clark (1903–83) were art historians and collectors whose ruthless intelligence, pictorial memory, eloquence in exposition and hard-won erudition were matchless in their fields. Berenson was the Lithuanian-born son of a Jewish pedlar, but got himself to Harvard, began transforming the study of Italian Renaissance art in the 1890s and, by his business with dealers and American collectors, made a fortune, which he spent on his luxurious Florentine villa, I Tatti, with its famous art library, and on princely hospitality. Clark, the only child of a boorish Edwardian parvenu, became one of the foremost public men of his time, made himself an outstanding television educator, bought a picturesque castle in Kent and received a peerage. Their letters, sent winging between London and the outskirts of Florence, will absorb anyone interested in the history of connoisseurship. They depict not only the unrelenting pursuit of intellectual and aesthetic excellence, but also that disciplined, unconfiding, self-respecting cordiality between intelligent people that today’s populists find stilted, frosty and superior. Each man, for example, knew that the other was a seasoned womaniser, but they both had the sense to keep their amatory exploits sealed in a separate compartment from their friendship.

In the mid-1920s Clark spent two years as Berenson’s pupil-apprentice, living at I Tatti and helping in a revision of the older man’s great work on Florentine drawings. Clark’s appointment in 1934 (aged thirty-one) as director of the National Gallery and his wife’s presidency of the Society of London Fashion