The centrepiece of this exhibition, Alma-Tadema's The Roses of Heliogabalus, seems a grand summation of Victorian art's predicament. It is such a feat of painting, and so exuberant, overflowing with observed details—there are surprising new colour harmonies; and the translucent marbles amaze us. There are the dopey facial expressions too; and all those details become distracting, weakening the composition, until their abundance overwhelms. But in a way—a different way—Alma-Tadema had actually meant to overwhelm us; we are supposed to succumb, aesthetically, to the mountains of petals he painted, in order to sense how Heliogabalus's guests, trapped under the petals, had themselves succumbed. The choice of subject-matter explains a great deal: here is a scene of absolute decadence which allows for absolutely decadent painting. The exhibition guide suggests that the spectator will "gradually discover the cruelty hidden beneath the decorative beauty of the scene".  And perhaps he will discover it, with some very generous imagining. For that cruelty is buried so deep beneath the decoration. The cruelty was less interesting to the painter—it was not really his subject. This is a picture of suffocation by prettiness, and it is presented as a Romantic dream. And there are baskets of real roses in the gallery, filling the air with their scent, matching the sickliness of the painting, and we feel ourselves suffocating too—not through beauty, which always provides vital relief, but through cloying aestheticism.

Romantic dreams have now changed. We may laugh at Victorian art; but is the art of today—with its cynicism and sloppiness—any healthier? The Victorian painters, however misguided, were unmistakably sincere in their ambitions. And they were far more serious than we are about the value of their craft. Those who sneer at them do so, perhaps, with not a little shame. If we are to laugh at the Victorians, we have also to laugh at ourselves. And there is a sadness in our laughter, for their lost talents and for our own.