Of all the lionised new British directors who have made it to the international big league in recent years perhaps none may be as overrated as Joe Wright.

He was he who made Atonement, adapted from Ian McEwan’s celebrated novel. His latest effort, The Soloist, is, by contrast, a mostly true story based on a book by Los Angeles Times journalist Steve Lopez.

Starting in 2005, Lopez wrote a series of articles about Nathanial Anthony Ayers, a schizophrenic homeless man he had encountered playing a two-stringed violin with astonishing virtuosity under a statue of Beethoven in a city park. Ayers, as Lopez discovered, had been a brilliant cellist whose talent had taken him from a Cleveland ghetto to the elite Julliard School in New York. But mental illness had brought him to the hard streets of LA’s skid row.

Over the next couple of years Lopez tried to help Ayers in various ways and with varying degrees of success (Ayers, it turned out, did not want an apartment or to take medication, though he was thrilled to hear an orchestra play again). Despite the frustrating gulf between the two men they eventually became genuine friends, as Lopez recounted in his columns which became a sensation and prompted the city’s mayor to pay more attention to LA’s huge homeless population.

It is promising raw material for a movie, with plenty of scope for a soaring classical soundtrack and some spectacular locations. And The Soloist does indeed make good use of the music, except in one absurd psychedelic animated sequence, and of downtown LA.

It is all surface, lacking in real feeling

However, despite this, despite a superb cast, despite imaginative cinematography and deft editing, the film just does not work. A story that should be so moving leaves you cold. It is all surface and technical cleverness but lacking in real feeling or insight.

Indeed, The Soloist is almost repellently slick. Just about everything is overdone and self-conscious and reeking of glossy self-satisfaction, from the repeated shots of LA from the air to the theatrical and obviously “designed” homeless shelter sets, to Robert Downey Jr’s ridiculous make-up when, as Lopez, he is supposed to have suffered a bad bicycle accident.

This lack of subtlety extends to the performances. Downey is one of the most brilliant actors working in film, indeed a kind of genius. Jamie Foxx is not only superbly talented, he is also a classically trained musician — an ideal candidate to play Ayers. Yet under Wright’s direction both here seem to be engaged in an acting exercise; their performances lack heart and heft. Worse, they enjoy no chemistry at all.

It does not help that the filmmakers turn the tall, middle-aged, and happily married Lopez of real life into a short, immature, divorcé who needs, and gets, a lesson in grown up commitment and relationships. This renders Ayers little more than a colourful catalyst for Lopez’s personal journey.

Most of the things added by Wright and Grant to make the real story more interesting actually make it less so. As played by Downey, Lopez has a shaven head and wears either a hipster’s pork pie hat or a hoodie. They have made him a rebel out of central casting when it would have been so much more dramatic — as well as true — if the journalist spending the night in skid row searching for his homeless friend were a conventional, tie-wearing senior writer.

Ayers gets the OTT treatment, too. Where all the other homeless mad people in the film — some of them the real thing — are dressed in the motley of regular street people, the costumers have given Ayers a special reflective vest sown with sequins. The problem is not just that photos of the real Ayers show an ordinary homeless-looking guy in an old army parka, but that the gaudy sequins make no sense in the context of his character or his environment. They are a filmmakers’ indulgence.

Joe Wright and his largely British team have wasted a superb cast and managed to render a powerful story trite and unmoving. They have also provided yet more evidence that no-one is as cynically “Hollywood” than a technically skilled English indie director given $60 million and invited to America.