The other day I ran into a most uncharacteristic painting by Turner. Entitled "The Gareteer's Petition", it shows a desperate-looking devotee of the muse seeking inspiration in his attic room, complete with unmade bed, a barrel-full of dog-eared folios and scraps of discarded paper. It's unusual in many ways: the scene is urban, indoor and unromanticised. The tone of the painting is hard to gauge; you might think (from the skew-whiff print of Mont Parnassus) it was satirical, in the tradition of Hogarth (and looking ahead to Daumier), but while Turner catches the obsessed quality of the poet, he doesn't seem entirely to be making fun of him.

A clue might be offered by the revelation (it was news to me) that Turner was himself a poet. The striking quality of truthfulness in the painting quite likely derives from Turner's own experience as an eager but not very successful versifier. Perhaps the best word for the tone of the painting is rueful. The obsession, the pain and the yearning are all real; so is the delusion, at least in that hopes of fame and glory are destined to be dashed. Turner spent many years writing a grandiose long poem entitled "The Fallacies of Hope", but he never finished or published it. All the same, he used quotations from the poem as prompts and titles for some of his most ambitious paintings.