IN THE LAST generation the output of high-quality art books has been transformed by modern colour-reproduction techniques and by outsourcing the printing to Asia. I notice that, in my own library, books on painting published before 1970 are now usually out of date, and unless they have a superlative text they have to struggle to keep a place on my shelves. (It is a different matter with sculpture.) Leading this ascent into excellence has been Yale University Press of New Haven, Connecticut (which also houses the great Paul Mellon gallery and research centre for the study of British art). Its art books are innumerable and nearly all worth possessing, and I must have about two hundred Yale volumes in my art library. In particular they put out marvellous catalogues raisonnis of the Old Masters, worth investing in since they are of the only kind of art book sure to keep its value. The latest, on Van Dyck's paintings, is of a high standard in all respects - text, reproductions, printing, paper and binding - and is a most enviable possession.

Van Dyck is the painter most admired by the English upper classes and has been ever since Charles I brought him to London in the 1630s. He is the one they most wish to see hanging on their walls. It is illustrative that, when Reynolds visited Gainsborough on his deathbed,