How do you write a biography about a man without revealing his identity?

It's a challenge that's been taken up by journalist Will Ellsworth-Jones in his new book Banksy: The Man Behind The Wall.

The book was released this month to widely positive reviews - the Guardian claimed it "reveals much of note about the notoriously elusive graffiti artist" and the Telegraph praised Ellsworth-Jones' use of "reporter’s initiative" in tracing Banksy's back story.

To help you make your own mind up, here's an exclusive extract from the opening chapter charting Banksy's daring infiltration of Tate Britain in 2003.

"One Wednesday in mid-October 2003 a tall, bearded man, looking slightly scruffy in a dark overcoat, scarf and the sort of floppy hat that cricketers used to wear, walked into Tate Britain clutching quite a large paper carrier bag.

Banksy, for it was he, walked straight past the security guards, who were probably more worried about what visitors might be taking out than what they were bringing in, and made his way unchecked up to Room 7 on the second level. It was a well-chosen spot that he must have researched beforehand.

For it is not a gallery you simply stumble into: there is no direct entry from a main corridor, you have to go through another gallery to reach it. It is usually quite quiet there, which allows the museum attendant to move in and out between galleries rather than having to sit covering just the one room.

Having chosen his gallery, next he had to choose his spot on the wall. He found enough room between a bucolic eighteenth century landscape and the doorway leading to Room 8 and claimed it for his own. He placed his paper carrier bag on the floor, dug out his own picture from the bag and then simply stuck it up.

It was a pretty ballsy thing to do; the Tate would not have been too happy to find a man stealing not their pictures but their space.

But perhaps his earlier years spray-painting the streets of Bristol helped steady his nerve, for he showed no signs of panic as he reached down into his bag for a second time and pulled out an impressive white stiff board on which was mounted the picture’s caption. This he stuck neatly beside his picture. And then he was off.

Banksy was once asked by an American radio interviewer if he carried out this sort of incursion alone.

He answered, ‘I do, yeah, you don’t want to bring other people into that.’ And strictly speaking he was right – he was the only man sticking the painting to the wall. But others were involved in the planning.

One of them remembers sitting with Banksy in a café going through the options: ‘We said to each other, “It’s like planning a bank robbery.”’

He had at least one accomplice and possibly more in the gallery, for we only know precisely how he achieved this coup because someone was filming him do it. Once the film had been mildly doctored so as to obscure his face, it went out on the web.

Eventually a set of stills were to find their way into his best-selling book Wall and Piece. As for the painting itself, Banksy said it was an unsigned oil painting he had found in a London street market. He claimed he found it ‘genuinely good’ but he was being kind; it was an uninspiring countryside scene with sunlight just managing to filter through the trees on to a meadow and what looked vaguely like a chapel.

Across the foreground of the picture he stencilled the sort of blue and white police incident tapes that you usually see keeping gawpers away from an accident. The picture was titled Crimewatch UK Has Ruined the Countryside for All of Us and the caption he stuck up alongside it was one of the first of Banksy’s many pronouncements:

It can be argued that defacing such an idyllic scene reflects the way our nation has been vandalised by its obsession with crime and paedophilia, where any visit to a secluded beauty spot now feels like it may result in being molested or finding discarded body parts."

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  • The Oscars refused to let Banksy come incognito to the ceremony in which his documentary Entry Through the Gift Shop was nominated because it was too much of a security risk.

  • Banksy says "I am unable to comment on who may or may not be Banksy, but anyone described as being 'good at drawing' doesn't sound like Banksy to me"

  • It's said that his agent isn't even quite sure of his identity

  • Celebrity owners of his art include Christina Aguilera and Angelina Jolie

  • One of the first conventional exhibitions of his art was held in a warehouse in 2000, but Banksy gave out only the street number for the building and not the street.

  • In September of 2006, Banksy inserted 500 fake CDs into the sleeves of Paris Hilton's debut release, at music retailers in several U.K. cities. Buyers bought his remixes of Hilton's songs, which were tagged with new titles, including - "Why Am I Famous?".

  • It is said his parents believe he is a painter and decorator rather than a successful artist.

  • The son of a photocopier engineer, he might have trained as a butcher but became involved in graffiti during the Bristol aerosol boom of the late 1980s.

  • In support of a Bristol anti Tesco demonstration he released a print which showed a smoking petrol bomb in a Tesco Value bottle

  • In August 2004, Banksy produced spoof British £10 notes changing the picture of the Queen to one of Diana, Princess of Wales's head and changing the text to 'Banksy of England'

Banksy: the Man Behind the Wall by Will Ellsworth-Jones is out now on Aurum Press priced £18.