What not to miss at London's Old Master auctions

July traditionally marks the Old Master season in London, with events such as the Masterpiece fair (until 3 July), Master Drawings and Sculpture Week and Master Paintings Week (both until 5 July) now clustered around the annual auctions. Our picks from the important evening sales at Christie’s and Sotheby’s show that this market continues to mount a challenge to the fashionable status of contemporary and Modern art. Selected by Paul Jeromack