Bridget Riley

Looking at Bridget Riley's paintings is like having a conversation with a particularly challenging tutor. Can't see the rhythms in her discombobulating patterns? Then train your lazy eyes to look harder. Don't like the colours? Tough, why should art pander to your pathetic ideas of taste?

That Riley, uncompromising during a five-decade career, is A Good Thing in the British art establishment, is not in doubt. And yet, as the septuagenarian comes up with more and more hard-to-like pictures, the point at which one is tempted to throw in the stripy towel draws closer and closer.

This show, for example, continues her study of almost impenetrably interwoven curved diagonals, developed across two large canvases and two wall paintings, all in a defiantly unlovely colour scheme of chalky ochres, lavenders, pale blues and green. The canvases introduce to the leaf-like forms rectangular elements that read like a shattered frame. The wall paintings reveal what happens when Riley's designs aren't constrained by the canvas edge - but are far from immersive.

In the back room a series of gouaches show some of the adjustments that take place before the assistants work up the designs. How rigorous, you might think, and how great to see an artist become more testing with age. I wanted to think that but the idea was ousted by the notion that, for the viewer, Riley's art is one of ever diminishing returns. Come on Bridget, throw us a bone.