Three stars

A postman's round in the mountainous regions of eastern France would have made a man fit and kept him that way. Walking alone for 32 kilometres a day with only the trees, the wildflowers and the birds for company, would not have sharpened the social skills, but it did heighten the imagination, and Facteur Cheval (Postman Cheval) seems to have liked it that way.

He walked the equivalent of five times around the world on his rounds.

In his spare time, Joseph-Ferdinand Cheval (1836-1924) created an astonishing architectural structure, inscribed with his very own words of wisdom, that has found its place in French cultural heritage. He is played by Jacques Gamblin in this latest film from Nils Tavernier whose The Finishers was released in 2013.

"What do you think about as you walk?" an attractive young woman, Philomene (Laetitia Casta), asks him one day. In typical fashion he walks off, leaving the question hanging until he follows up with an answer on another occasion: "I dream."

After an improbably short courtship, Philomene, a widow, became his second wife. Cheval had also been widowed when his first wife died. The young son from that marriage was put in the care of relatives because the postman was reckoned either unable to support him, or unfit and a bit of a nutter, or both.

Cheval was seriously inhibited and reclusive, but not entirely. The impression we also get is of someone who would have liked to see the world.

His boss would pass postcards on to him and he was an avid reader of magazines about far-away places where his imagination could run riot - places like the newly rediscovered temple complex of Angkor Wat in today's Cambodia, the Mayan temples of Central America and the pyramids of Egypt.

How would it have been to see photographs of places like that, when the sleepy hamlet of Hauterives and its inhabitants was all you knew?

And still Cheval never travelled in his long life.

This odd, solitary character, who is played with a gritty determination by Gamblin, decides to build a palace for the new baby daughter that Philomene has given him. He will build it out of the unusual stones he has picked up on his rounds and ferried back home in his wheelbarrow.

It is an impressive and touching gesture from a taciturn man who has endeared himself to few.

The project took hold and dominated his life. The stats reveal that Cheval was one of life's true eccentrics. After a 10-hour day doing the rounds, he would spend a further 10 hours on his palace, a routine that he maintained with nothing short of ferocity for 33 years. He has inscribed in stone on his edifice that it represented 93,000 hours of work.

If you don't go to see this film, it is well worth having a look at the Palais Ideal du Facteur Cheval online, a fantasy building born of a pure impulse, inspired by his tiny new daughter, Alice. Tragically, she died at 14, but he eventually resumed his project, the design of which combined the Brighton Pavilion, Angkor Wat and goodness knows what else. It has to be seen to be believed, and apparently draws 170,000 tourists a year.

With the given facts, it looks very much like Cheval was on the spectrum. Asperger's comes to mind, but how would we know this of a person who lived in the late 19th and early 20th century, before the perspectives of modern medical science?

Other treatments of men with autism spectrum disorders have been more engaging. Dustin Hoffman was memorable in Rain Man, as was Russell Crowe as a mathematical genius in A Beautiful Mind. The Australian film Black Balloon, with Luke Ford as a boy with autism, was very good too.

Despite the felicity with which The Ideal Palace is put together, despite the astonishing and impressive obsession of the main character, and though it proposes that the isolation in rural France in the past was both a blessing and a curse, it isn't as compelling as it wants to be. This biopic of an artist is on the long side, too.