Why British art is alive and well in Belgium

Want to see British art as you've never seen it before? Then you'll have to go all the way to Belgium, says Tom Lubbock. But this must-see show is worth the trip

Empiricists! Visionaries! Comedians! The strengths of British art lie on the margins. Where we've excelled is in minor or eccentric genres: documentary observation, dream worlds, caricature - the kind of work that has often been discounted as mere factual recording, or fantasy, or farce. And even now, when hierarchies are shaken, it doesn't get its due.

We're still brought up to think it's the big blurry ones, the masters of Romantic landscape, Constable and Turner, who matter most. Other talents, such as Hogarth, Stubbs, Blake and Gillray are, of course, admired. Yet even they remain curious byways to the true highway: the eventual triumph of heroic landscape painting, which (as the story is normally told) is the point at which British art, stunned for centuries by image-hating Protestantism, can finally hold its head up on the European stage.

But suppose you told the story differently. Suppose the weird and provincial aspects of British art were given the lead. Suppose those three strands - comedy, mystical imagination, the close observing of nature and society (and the frequent overlaps among them) - were taken as the dominant line. What then? Well, suddenly British art makes sense, and catches fire.

You needn't take my word for it. At last there's an exhibition that tells this story. It's not a British exhibition, and it probably couldn't be. It's on in Belgium. British Vision - Observation and Imagination in British Art 1750-1950, at Ghent Museum of Fine Arts, gives you British art as you've never seen it before.

It's a huge display, over 300 works, and at first it may simply seem generously inclusive. It's a show with room for both an intense rock study by Ruskin and a nonsense illustration by Lear. It embraces Aubrey Beardsley and Ben Nicholson. It hangs L S Lowry in sight of Francis Bacon. But after a bit, you realise that it is actively tendentious.

The usual orderings are being overturned. The old highway is largely ditched, and the byways take over, in what Robert Hoozee, the curator, identifies as "a succession of alternative moments", "a marginal tradition" - an alternative, that is, not only to the normal story of British art, but to the priorities of European art history as a whole.

First sign that something is up: the absence of portraiture. If you know the sequence of British art from, say, the historical part of Tate Britain, you'll expect it to start with rooms of portraits: Tudor portraits, Stuart portraits, Hanoverian portraits, plus park paintings. In Ghent, all that goes. We start abruptly in the 18th century, with Hogarth's anti-portrait, Sarah Malcolm in Prison, a brilliantly alive little painting of a convicted murderess awaiting execution, a pointer to much documentary painting to come, such as Holman-Hunt's Work, William Roberts' The Cinema, David Bomberg's Ghetto Theatre.

The show pursues its argument through pointed inclusions and exclusions. Joshua Reynolds, founder of the Royal Academy: out. All those hapless attempts by academicians to do high-allegorical and narrative painting: out. Gainsborough: almost out. Constable and Turner: definitely in, but represented by smaller, more observational work, not by their big statements.

There's a good section, which could be bigger, on British Humour. Here you start to notice the interesting overlaps between categories. Hogarth's satire in The Rake's Progress is rich in documentary observation. Gillray's caricatures are on the brink of the apocalyptic, and Fuseli's images of female hairdos are fashion-satire becoming perverse sexual nightmare. Similar ambiguities continue into Richard Dadd's fairy pictures, and Edward Burra's unplaceable Rye Landscape with Figure - well, I call it unplaceable, but the point of the show is to give it a place, to show its mixture of caricature/dream/documentary as a characteristic British mode.

The meticulous recording of nature is another major theme. The show succeeds in reframing the British landscape watercolour, which no longer looks like a cautious prelude to the power-performances of Constable and Turner. It is something with its own power, the force of intense observation, whether that appears in Luke Howard's pioneering studies of cloud shapes; Thomas Sandby's tracking of a comet; or Thomas Girtin's explorations of distance. Again, overlaps arise. How far are Francis Towne and John Sell Cotman, with their analysis of landscape into distinct coloured forms, from the heightened perception of Samuel Palmer, where every natural form is filled with spirit?

Blake, the patriarch of the visionary line, of course gets a lot of emphasis. So do the Pre-Raphaelites, and later on, Stanley Spencer. They fit the bill perfectly: close observers of the natural world, with an active vein of fantasy. But both the Pre-Raphaelites and Spencer are also still a source of embarrassment for some, marked with a fatal touch of whimsy. Therefore they make a good test case for this show, one of whose objectives - undeclared but clear - is to redeem such dodgy peculiarities, make them look like strengths, and continuous with other art of indisputable standing.

The general quality of the works chosen is impressive. Just to mention some highlights: Stubbs view of Newmarket Heath; Thomas Jones's Buildings in Naples; Joseph Wright's Arkwright's Cotton Mills by Night; John Russell's Telescopic Study of the Moon; one of Constable's most beautiful cloud studies, and his Elm Tree Trunk; Blake's The Sea of Time and Space; Dadd's sketch for The Faery Feller's Master Stroke; Ford Maddox Brown's The Last of England; Ben Nicholson's Mousehole; Paul Nash's Vernal Equinox.

But what makes the show's story work is not just this parade of excellence, it's the constant opportunities for interconnection it creates, and the relay of energies that pass from picture to picture. It's startling achievement is to make British art look fanatical. And if you want to know the difference, then in London, at the moment, you can find a telling contrast. A Passion for British Art, at the Royal Academy, has works from the collection of American Britophile Paul Mellon. There are some terrific pictures that might equally appear in Ghent, so why in comparison does the RA show seem a stately bore? Because there's just enough stiff, stuffy work there - portraits, portraits - to neutralise the connections and energies that the Ghent show activates.

The RA show stops mid-19th century. The Ghent show continues to mid-20th, and consequently faces the issue of modernism. How will this account of an alternative tradition deal with the Continental modern movements and their undoubted influence on British art? Interestingly. Impressionism: ignored. Cubism: recognised, but understood as a fantasy style, a form of Blakean visual variation. Abstraction: almost ignored, except again as a visionary mode (the British line is essentially figurative). Surrealism: unnecessary, since Britain has had a native strain of surrealism long predating the movement.

But I am puzzled as to why there is so little of Wyndham Lewis, especially his images from the 1920s and 1930s. They seem textbook examples for this show, with their sharp compound of modernism, satire and fantasy. And I could mention other strangely missing names: Flaxman, Bewick, Beerbohm. Generally, there could be more cartoonists, illustrators, and vernacular/folk art. But this is only to say that, with a marginal tradition, there will always be further margins.

The strength and weakness of this marginal tradition, whether in comic or visionary or empirical mode, is its capacity to create its own worlds. These images make little contained worlds and inhabit them - the art of an island nation? That is the source of their intensity, and also a limitation. British Vision runs a risk of seeming childish, safe, escapist, twee, jokey, whimsical. At least, this is one of the many questions raised by this ground-breaking, must-see exhibition.

British Vision - Observation and Imagination in British Art, Museum of Fine Arts, Citadelpark, Ghent, to 13 January