There’s a moment during slippery, chameleonic (mock?) documentary Exit Through The Gift Shop when someone says: “I think the joke’s on … actually, I don’t know if there’s even a joke.”

It’s a revealing admission that sums up (as much as anything can) street artist Banksy’s directorial debut, a true one-off that will leave you questioning whether you’ve been conned as much as the hype-happy media and gullible sycophants who fawn over the art world’s self-proclaimed next big thing, Mr Brainwash.

Asked at the start of the film what it’s about, Banksy responds: “It’s about a guy who tried to make a documentary about me, but he was a lot more interesting than I am, so now the film is kind of about him.”

That man is Frenchman Thierry Guetta, an LA-based compulsive videographer who we learn from Rhys Ifans’ incredulous narration stumbles across the burgeoning street art movement through his cousin, an internationally recognised graffiti artist called Invader. He documents Invader going about his legally dubious business and is introduced to many of its major players, in particular Shepard Fairey, whose trademark tag of ex-wrestler Andre the Giant with the word ‘Obey’ underneath has been become so iconic “it gains real power from perceived power” (he’s equally well-known for designing the famous Obama ‘Hope’ poster which came to represent their 2008 presidential campaign).

When Banksy arrives in LA, Thierry excitedly hooks up with the elusive artist and, following a colourful episode in Disneyland involving a Guantanamo Bay detainee doll, the two become trusted friends. After documenting Banksy’s wildly successful show Barely Legal (part of which involves painting an elephant pink as a statement about how we ignore the things right in front of us, apparently), Thierry turns the thousands of hours of footage he has into a 90-minute street art film called Life Remote Control (trailer below), which Banksy writes-off as “shit” and made by someone “with mental problems”.

He takes the footage off Thierry’s hands and suggests he give street art a go. Running with the idea, Thierry reinvents himself as ‘Mr Brainwash’ and, with the help of a team doing all the work, a promotional soundbite from Banksy (“Mr Brainwash is a force of nature, he’s a phenomenon. And I don’t mean that in a good way”) and a ravenous media, slaps together the show Life Is Beautiful that’s as creatively bankrupt as it is crowd-pleasing.

Opinions are split on whether the film – marketed as ‘The world’s first street art disaster movie’ – is one giant prank on Banksy’s part or that Thierry really did suddenly transform himself into Mr Brainwash and become an overnight sensation. Some have even posited the theory that Thierry is actually Banksy hiding in plain sight, a pink elephant so to speak.

Banksy has always maintained the film is real, although Thierry in an interview with the LA Times admitted of his Mr Brainwash persona: “In the end, I became [Banksy’s] biggest work of art.”

That being said, a revealing moment at the start of the film suggests there’s plenty of Thierry in Mr Brainwash. Talking about his time as the owner of a retro clothes store in LA, Thierry admitted he would buy items cheap, rebrand them as designer and sell them on to the hipster brigade (including alt-rock musician Beck, who’s caught on camera) at hugely marked up prices. It’s an approach he adopts for Life Is Beautiful and one that cleverly throws a spotlight on the value we place on art, especially when it’s in fashion.

The influence of hype on a gullible public is also satirised. One punter queuing for the show says “I’m not quite sure what I’m here for, but I’m excited about it,” while another gets a bad case of hyperbole when she ecstatically calls Life Is Beautiful “a triumph … it will go down in history”.

Away from the vacuous sycophancy, Thierry comes across as a buffoon, all be it a likeable one. When he isn’t walking into lamp-posts or accidentally tipping paint over the back of his car he’s described as “retarded” or a waste of space and lambasted for not having a clue, which kind of adds to his charm.

Whether Thierry/Mr Brainwash is the real deal or an elaborate practical joke is ultimately irrelevant, what counts is that Banksy has conjured up a playfully provocative work of art in and of itself.

“Maybe it means art’s a bit of a joke,” he says. Watch Exit Through The Gift Shop and make your own mind up.