Three to see: London

Want to know which artists Van Dyck, Matisse and Lucien Freud collected? Painters Paintings (until 4 September) at the National Gallery sheds a light on the collections of eight painters, some of whom collected each other. The show, which opened yesterday (23 June), includes Picassos Portrait of Dora Maar (1942), which he sent to his rival Matisse as a get-well present. If the British summer fails to materialise, there is always the South London Gallerys Under the Same Sun: Art from Latin Ameri