I’d just got used to the idea that Swedish mystic Hilma af Klint had pioneered abstract art years before Kandinsky, Mondrian and Malevich when I found out Georgiana Houghton, a Victorian English medium, got there first by several decades with a series of bizarre but beautiful “spirit” paintings. She claimed her hand was guided by great artists from history and even by St Luke. But even if you laugh off the idea, there’s no doubting the astonishing originality of these pieces, which tremble and shimmer with colourful swirls and lines and pious symbols. Barmy? Possibly. But it’s worth remembering af Klint, Kandinsky, Mondrian and Malevich were all followers of another odd cult, Theosophy. Check out Houghton’s works at the incomparable Courtauld Gallery till September 11.