In a somewhat stark meeting room at Tate Britain, the curators of its forthcoming L.S. Lowry show, T.J. Clark and Anne M. Wagner, are attempting, at my request, to extol the artist's virtues to me. It's a complicated business. For one thing, I have the impression that they regard enthusiasm as infra dig. "I'll give it a shot," says Wagner, reluctantly. "But I don't think you're going to be convinced."