Despite competition from scores of rival mechanical toys and artworks, including a crow that reads all the rejection letters received by one artist, and a tiny Fabergé elephant owned by the Queen, when the bell rings every staff member, volunteer, curator and visitor within earshot drifts towards the gallery at Compton Verney where an eccentric masterpiece creaks and whirs back to life.

Rowland Emett, the cartoonist, designer and inventor who created the flying car for the film Chitty Chitty Bang Bang, spent years on A Quiet Afternoon in the Cloud Cuckoo Valley but never saw it completed. He first built a fantasy railway line for the 1951 Festival of Britain, but believed Quiet Afternoon his greatest work, a glorious summer outing on the Far Tottering and Oyster Creek railway, complete with butterflies and birds, a driver toasting crumpets at the firebox, a fisherman catching a mermaid and a farmer playing the harp to his cows.

By the 1980s it had become a lament for the lost glory of the British railway: the bell which rings once an hour to signal that the 10 metre sculpture is starting up has precisely the wistful note of a country church bell chiming across fields. Curator Antonia Harrison pointed out that Emett lived in the same village as Dr Richard Beeching, the man blamed by many for the death of the rural railway network.

A Quiet Afternoon in the Cloud Cuckoo Valley, 1988-89, Rowland Emett. Photograph: James Bastable

Harrison explained that the piece was intended for a shopping centre in Basildon, but never installed. A collector bought it after Emett’s death in 1990 and the piece was then stolen from storage and sold to a scrap metal dealer, who realised it was extraordinary and called the police. It took volunteers three years to restore it to full working order. “It just makes you feel happy,” Harrison sighed, as the last notes sounded and the wheels stopped spinning.

The exhibition grew out of a modest project to restore a little automaton from the museum’s Folk Art collection, Model of a Potter’s Workshop, which Harrison thinks was made around 1900 as a shop window attraction. It grew into a look at the centuries-old fascination with machines that seemed on the cusp of human life, shading into today’s unease over robotics and artificial intelligence. The contemporary artist Tim Lewis had to master a sewing machine to create his sinister crimson glove on an animatronic hand, and Harrison Pearce’s unnerving piece reflecting six months he spent being tested for a brain tumour – it turned out the scans had been misinterpreted.

Many of the antique pieces in the exhibition are too fragile to operate, and they haven’t had the nerve to wind up the Queen’s Faberge elephant which apparently walks and flaps its ears: securing the loan included sending the cushion on which it lies to Buckingham Palace for approval. When the curators unpacked its modest wooden travelling box, they found a scrap of paper, possibly dating from the jewel studded piece coming into the Royal Collection in the 1920s. In tiny handwriting, it bore truly regal instructions: “To wind up the elephant push up the third diamond on the left side of the saddle. To start it release the gold spring underneath the elephant.” The curators yearn to try it.

