Bridget Riley, famous for paintings of colour and pattern that zip, swim and sing before your eyes. Flashing stripes, circles, triangles and ellipses that fool the eye into thinking that there are moving shapes on the canvas. Sometimes the strobing effect is so intense, you might have to look away. While Riley’s paintings of this kind are well known, just opened in a room in the National Portrait Gallery are some of her little-known sketches. Read full article.