Visual Arts: While shepherds ignored their flocks

The familiar view of Constable's Cornfield may not be as idyllic as it at first appears. By Iain Gale

On 8 April 1826 John Constable dispatched a painting from his studio to the Royal Academy. "I do hope," he wrote to his friend, the Revd John Fisher, "to sell this present picture - as it has certainly got a little more eye-salve than I usually condesend [sic] to give them."

Sadly, despite being shown again in London, at the Paris Salon of 1827, at the Birmingham Society of Arts and even at the Worcester Institution, the picture did not sell until 1837, some months after the artist's death, when it became the first work to be donated by public subscription to the new National Gallery.

The slow uptake has not, however, been reflected in the picture's later popularity and Constable's words have taken on an unimagined significance. In The Cornfield, Constable had made more than a painting - he had created a national icon with the power to "salve" not only the eye but the soul.

A new exhibition at the National Gallery examines the enduring significance of this extraordinary work, which has, over the past 170 years, been used to adorn everything from biscuit-tins to wallpaper. In a slightly trainspotter- ish exercise, Colin Painter, principal of Wimbledon School of Art, has gathered an assortment of these gewgaws and canvassed comments from their owners.

Inevitably, as acquaintance with Walter Benjamin's The Work of Art in the Age of Mechanical Reproduction might suggest, the general effect is to diminish the painting, to rob it of its aura. That, however, makes this show no less telling an account of the way we look at pictures.

For many, Constable's Cornfield is the very essence of England - a vision of a lost utopia (which, perhaps, only ever existed in our imaginations). Read your way through the painting: on a country lane - Fen Lane, between Dedham and East Bergholt - a shepherd boy pauses to sip from a stream while he lets his dog herd the flock towards distant water-meadows; in the mid-distance, a farm labourer passes before a field of standing wheat; beyond rises the reassuring presence of a church tower.

Hardly surprising that unemployed engineer Don Hazelgrove should consider it "a record of England" or that it should transport charity worker Su Stanton "back to an era when there was an age of innocence". But just how much of an idyll is The Cornfield? Looked at another way, Constable's masterpiece is an icon not of beauty and nationhood, but of self-deception.

Among the many interpretations advanced for the picture's uncharacteristic iconography, one seems more than usually convincing. Look again at the image: the boy has abandoned his flock and his duty; his collie, too, is distracted (by a woodpigeon in a tree); the sheep are left to wander leaderless. Look beyond them: the gate into the field has come off its hinges, and a plough has been abandoned (presumably, since this is midsummer, for some months). The three labourers we can see in the field would barely be enough to harvest it. So what is going on? Surely Constable, however much it might be out of character, and for all his stated intent to "salve the eye", is here constructing a visual metaphor.

Cleverly, he confounds potential criticisms of the painting as a purely illusory landscape by giving it the palpably real setting of the very lane along which, as a boy, he had daily walked to school.

Looking beyond the scene's initial power to "salve" the eye, we are drawn to ask "what happens next?" Do the sheep trample the corn? Does the lack of labour make for a poor, late harvest?

Constable's menacing narrative contains a promise not of rural stability, but of potential chaos. It seems both ironic and pitiable that this portent should today be taken for a vision of Arcadia.

n At the National Gallery, London WC2, to 21 April