As that remark shows, however, Orpen, a protestant Irishman, was the victim of the English resentment of earned success and of an increasing populism which intensified English puritanism.
Orpen's radiant colours and his luscious textures celebrated not only wealth but sensuality, a quality that seemed unnatural when not speaking Italian or French.
One indisputably English - and Irish - quality Orpen had, though, was irony. The young woman on a sofa in Sunlight, facing the window, wearing only the stocking she is raising one foot above her head to pull on, could be a rich girl in her charming home or a maiden opening her legs to Apollo. The portraits of his contemporaries are full of searing jokes. William Nicholson is commanding but aloof, a patriarch who has sucked all the life out of the dining room where his children sit like demoralised marionettes, his blankly staring wife is pasted on the rear wall, and the baby has been turned into a sardonic dwarf.
Orpen sometimes engages in a teasing game with the viewer. See how long it takes you to notice the flashes of red in several of his paintings, even when they are in the conventionally most distracting position, close to an edge. When one's eye has made the leisurely journey round Early Morning, slipping past ivory sheets, rosy flesh, and golden hair, it stops - bang! - against adjoining shapes of red, black, and screaming chartreuse.
In a more sober age, this bravado probably counted against Orpen, as did his showy virtuosity. The paintings on view could be a series of questions in a name-the-influence quiz: a brown-toned laundress, humble but feminine (Chardin); a backlit figure beneath a bleak, shadowed arch (James Pryde). A scene of rollicking peasants includes, along with a white-faced Goya dancer, a reproduction of Hogarth's Shrimp Girl. One of Orpen's allegories (not his best work: they look like a bunch of art students and pin-up girls in fancy dress) has a magpie, for bad luck, perched above a figure he disliked. But the magpie itself is disliked - to future viewers versatility would be equated with insincerity.
Orpen was affected by the First World War, in which he was an official artist, but not in a good way. The products of that experience are the weakest here, a crazy jumble of styles and palettes. Dead Germans in a Trench, with its pink snow and pistachio-faced corpse, would not be out of place in a boudoir, and in other paintings horror is expressed by drenching the subject with a nasty, comic-book viridian. Worst of all are the single and group portraits of soldiers, which evoke an artist Orpen would never have summoned up intentionally - Norman Rockwell. There are more than enough paintings in this exhibition, however, to show us why Orpen was regarded as impressive and enchanting. And, if you want relevance, look at one of his nudes sprawled at the edge of a bed or posed against hills of crumpled linen and think of Lucian Freud.
To 2 May (020-7416 5320)