"The rolling English drunkard,” wrote GK Chesterton, “made the rolling English road.” We could add that the bonkers British eccentric makes some bonkers British art. This country’s proud history of art and literature has been swelled both at the margins and, in some cases, right at the heart by the work of writers and artists who are not quite like the other ducks. And a new exhibition at the Dulwich Picture Gallery puts a welcome focus on one strand of that history – in the form of a celebration, 100 years on, of British Surrealism. That, perhaps, should be surrealism with a small “s” as well as a capital one. For as much as the exhibition examines the self-declared Surrealists of the early 20th century, it also ranges back as far as the early modern period to trace the “ancestors” of their work, and finds a common sympathy between artists more usually kept in separate categories. We know the surreal when we see it....