No sooner had the scale model for one of the world’s largest pieces of public art been unveiled than a schoolgirl volunteered the question that no one else dared to ask.

Stooping to inspect the underside of the horse that will ultimately become a 50-metre (160ft) tall statue, the curious pupil asked: “Is it a boy horse?”

Katie Blackwell, 12, who is enrolled at Swan Valley Community School, where the unveiling took place, quickly deduced that it was a stallion.

Mark Wallinger’s sculpture was announced the winner yesterday of a competition to design an artwork to mark the building of Ebbsfleet International station in north Kent and Ebbsfleet Valley, a new town between Dartford and Gravesend.

The 25,000 residents of the new town will not have to stoop. They will have to adjust to opening their curtains every morning to be greeted by a sculpture that Wallinger claims will be a “faithfully accurate representation” of a thoroughbred stallion.

Passengers aboard Eurostar and motorists on the A2 may be impressed by the scale of the horse that looms over them. Each hoof will be the size of a bungalow, each eye the length of a pillar box and each testicle the volume of a people carrier.

The artist, who won the Turner Prize in 2007 for his recreation of an Iraq-war protester’s display, told The Times that his design was based on a racehorse of which he was co-owner. “I own half of a leg of Riviera Red,” he said. “It’s actually running today at the 2.40pm at Lingfield.”

It was Wallinger’s lucky day. Not only had his horse won him the commission but it also came in first on the racetrack at odds of 11-2.

Mark Davy, whose company Future-city is curating the project, said that the horse had to be 50 metres tall to comply with the Highways Agency. “You have to be able to see it from a long way off. It would be too distracting for drivers if they came round a bend and suddenly saw a giant horse.”

The statue has already cost its sponsors £1 million to commission and is likely to exceed £2 million to complete. Land Securities, Eurostar and London & Continental Railways would not commit to a finishing date, but admitted that Wallinger’s hope to finish by 2012 was wishful thinking.

Wallinger, 49, hopes to build it out of fibreglass and reinforced concrete, but is unsure because no one has attempted a project on this scale. He hopes that it will last at least 70 years. “It will be built to last and then it will be down to a generation or two down the line as to whether they want to keep it.” He said that there would be a maintenance programmed but he was unsure how it would be kept clean.

Wallinger, whose design beat a polygonal bird’s nest and a series of cubes with a laser shining through the middle, hopes that the horse will appeal as a beautiful animal and as a symbol. It will represent the county of Kent, whose logo is a rearing horse, and the merging of cultures. “It is a very English horse but we did it by importing three Arab horses. It’s a symbol of import-export and immigration and emigration. It has a bridle on it to suggest that we [mankind] had some kind of input. Humans find horses more beautiful than most other animals. I liked that the aesthetic of the piece had already been worked out over the centuries by horse breeders.”

Residents of Swanscombe, the nearest village to the site, were largely indifferent to the prospect of their view being dominated by a 50-metre horse. The present site is a green but unpleasant wasteland studded with electricity pylons, chimneys and dockside cranes. The nearest cultural landmark is the Bluewater Shopping Centre.

Sheila Harris, 61, said she hoped that it would be nicely done. “I’m glad it’s not one of those angel things,” she said, referring to Antony Gormley’s Angel of the North in Gateshead. “Everyone can relate to a horse.”

Katie Blackwell, the observant pupil at the unveiling, was more enthusiastic. “This was my favourite design. I’ll be able to see it from my house.”

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