Modern painters: The Camden Town Group, Tate Britain, London

Call it a fairly quiet revolution. In 1911, a group of male painters – Walter Sickert, Robert Bevan, Malcolm Drummond, Spencer Gore and others – came together in London to define what looks, with hindsight, like a pragmatic English response to continental developments in painting – to Post-Impressionism, Fauvism, Van Gogh, Gauguin and others.

A number of this so-called Camden Town group lived in north London, and the paintings they made, all within the realist, figurative tradition, helped to document, and redefine, the nature of the metropolis itself. The group exhibited together for a brief period – about 18 months. With the onset of war came new movements; vorticism was one. The art of the vanguard became starker, more mechanised, more brutalised.

So, for the most part, don't expect to be enthralled by the shock of the new in this show. There is experiment, but it is by no means as radical as that of its French predecessors. It represents a kind of catching up with what had been happening overseas – with the use of bold and unnatural colours, for example, or the way in which a painting can be both a depiction and an exercise in pure decoration.

Only one painter, Sickert, is truly shocking, and he was only one-quarter an Englishman – his father was Danish, his mother Anglo-Irish. Sickert towers above the rest of the painters in this exhibition, for various reasons. His paintings of the female nude were brazen and provocative, and seem so even today. He painted female flesh in the raw, lumped across grubby iron bedsteads, in the murkiest of lights. Gone completely was that questionable Victorian passion for showing women as ethereal beings.

Nor did he apologise for what many of his critics regarded as flagrantly tasteless, if not downright immoral, renderings of the female form. In fact, he positively sought out publicity. One group of paintings was called The Camden Town Murders. He chose the title to associate his paintings with a celebrated murder mystery that engulfed the front pages of the Daily Mirror – you can see facsimile reproductions of some of these pages on the gallery's walls. It provoked outrage – and Sickert was delighted.

Other paintings by him in this show demonstrate his powers as a commentator on working-class entertainment – the music hall, the end of the pier show. Perhaps the saddest canvas by Sickert in the entire show, dated 1915, shows a troupe of clowns and comics performing, at dusk, on the pier at Brighton. Half the deck chairs are empty. The gas lighting, a strangely glaring pinky-blue, has a ghastly, almost acidic, ominousness about it. The clowns look as if their diminished forms are barely sufficient to bulk out their outrageously comic costumes. Somewhere just over there – within earshot, when the wind is in the right direction – the guns of France are booming, heartlessly.

In another painting by Sickert, Gallery of the Old Mogul, we see scarcely anything but the dark backs – so dark as to be barely visible – of spectators standing in the gods at the music hall. The excitement, emphasised by the murky tones, is steamily bovine.

The date is 1906, well into that gloriously prolonged Edwardian summer before the Great War snuffed it all out. Sickert's paintings show us a London bereft of such glamour, stripped bare, often nasty, damp, dingy and impoverished.

To 5 May (020-7887 8888)