I've got to admit that there are times when a little of art commentator Ben Lewis goes quite a long way. I can feel myself resisting the faux-naif persona complete with hat (above) and -- although he seems mostly to have grown out of this -- big fluffy mic. So I was a touch sceptical at the start of BBC Four's The Great Contemporary Art Bubble (on iPLayer for another 6 days). We knew there was too much money in the contemporary art market, right? And that that market has been buffeted and bruised in the past months. So did we need another film about it all, especially when Robert Hughes' The Mona Lisa Curse for Channel 4 last year had elegantly tilled some of this ground? But in fact the film is smart, entertaining and strikingly tough in its analysis.

Directing as well as presenting, Ben Lewis journeys through the art world in his oh-so-wacky electric car, which at the start he has customised by artist Tobias Rehberger. He's on a mission to understand how prices for contemporary art spiralled up in the past ten years even though (or because) 'much of the art was repetitive, mass-produced and commercial'. Among his guides are New York Times reporter Carol Vogel, journalist Scott Reyburn, economist Edward Chancellor, art market commentator Josh Baer and -- best value by a neck -- hedge fund manager Jim Chanos.

The bad guys in the story are, primarily, the auction houses who, it is alleged, have propped up prices, offered guarantees to sellers and lent money to buyers. In the process, as Chanos explains, 'they stopped being agents and became principals again'. Which, as the real estate market has shown, was a dumb thing to do.

Working alongside them have been the galleries, and perhaps inevitably Ben Lewis' focus in the second half of the film is on White Cube and its relationship with Damien Hirst. One story is about the artist's notorious 'diamond skull', an artwork called For the Love of God, 2007, which was put onto the market for a quoted price of £50 million and seemingly sold. But then it was revealed that the artist and his representatives were part of a syndicate that had bought the work, which Chanos compares to 'a failed underwriting'.

That was a tale already out in the world, but what I think had not been revealed before is that it was Ben Lewis who last autumn secured a leaked inventory from White Cube. This was allegedly of works by Damien Hirst that the gallery had in stock. He in turn gave this to The Art Newspaper (editor at the time Cristina Ruiz is a consultant on the film) which got a lot of play from the scoop just before the Sotheby's auction of Damien Hirst artworks in September.

Accusing him of being biased against contemporary art, Sotheby's refused Ben Lewis's camera access to the auction and he had to be content with watching from a side room. As he leaves he confides to the screen that it was all a bit like watching the band play as the Titanic went down. This after all was the day when Lehman Brothers collapsed and Black Monday was the Evening Standard's headline.

None of this sharp journalism needs the fripperies of the former Lewis style, and he does just as well in his visits to investors and collectors like Aby Rosen and Alberto Mugrabi. Billionaires, Lewis contests, 'were effectively hijacking art history with all their money'. His encounters are revealing, not least because for the most part they are played straight with only a mite of mugging -- although I was a bit bemused by his throwaway thought that 'neon is the cheese sandwich of contemporary art'.

The main auction houses turned down Ben Lewis' requests for interviews, as did White Cube and Damien Hirst and his representatives. So too did Nicholas Serota and Tate when he wanted a response to his argument that the public is subsidising the art market through our museums. And the Metropolitan Museum of Art refused him permission to film their rooftop show of Jeff Koons' work last summer.

Much of the actual artwork in the documentary is artfully filmed in situ and in part only so that fees and permissions can be negotiated around -- and in the closing credits there's a long list of title acknowledgements in almost unreadably small type presumably to meet the 'fair use' obligations of the 1988 Copyright, Designs and Patents Act. The film's own graphics are great.

Some conclusions: 'Greed and fear run these things.' (Jim Chanos) The contemporary art market through to last autumn was 'the epitome of the vanity and the folly of our age'. (That's Ben) And this is Jean Baudrillard, quoted in a closing caption: 'Art does not die because there is no more art. It dies because there is too much.'