A sculpture of this scale, and so strong a statement on the British landscape, must be a populist piece to its core. It does not have to be about the avant-garde, but about sculpture in its most powerful, evocative and easily understandable form.

This is where Mark Wallinger has stolen the march. Of the proposals outlined yesterday, his white stallion is all the more striking for being instantly recognisable. Horses are a part of the British way of life, far more than interlinked polyhedrons, cubes, lasers and spatially inverted castles. It requires no footnotes to glean its meaning.

The horse will articulate the landscape, and a work on this scale is as much about the landscape as the piece itself. Its location is not only astride the Garden of England, but also the Gateway to England — to be seen by people in their thousands every week, in minutes, even moments, as they travel by train, and road, between London and the Continent.

Those commissioning the work have suggested that it must stand up for the nation, and, literally, historically and metaphorically, Wallinger's horse does just that. It echoes Stubbs's famous painting Whistlejacket - an icon of English painting — and could claim a place as a three-dimensional, 21st-century likeness.

When the shortlist of candidates was announced this year, his name stood out as the most consistently unpredictable, least stuck on style. The other sculptors —Turner Prize winners, recipients of the Lion d'Or — all have proved their artistic credentials in the past. Yet while their offerings do not underestimate the importance of impact, the messages are too alien, too subtle.

Daniel Buren's five-cube structure is the closest to offering a personal appeal — mixing its otherworldliness of mirror-polished stainless steel with the reflections it would give out of people and skies. Whiteread's fairy-ish house silhouette, perched on its recycled mountain, is too delicate; Deacon's nest of steel latticework, too much like a confusing roadmap.

While Le Brun's offering is monumental, the artist, famous for his horse works, perhaps should have stuck to his old script. For it is Wallinger that wins it for me. It is a fresh vision, but imbued with vital familiarity. And in the confusing world of modern megalithic sculpture, what could make more sense than a horse in a field?

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