see more

LONDON, ENGLAND - MARCH 23: An employee holds Banksy's 'Girl and Balloon' which was painted on an Ikea frame at Bonhams auctioneers on March 23, 2012 in London, England. The painting, estimated at GBP 15,000 - 25,000, USD 24,000 - 40,000 and 18,000 - 29,000 euros, forms part of the Urban Art Sale, which takes place at Bonhams on March 29, 2012. (Photo by Peter Macdiarmid/Getty Images)

LONDON, ENGLAND - MARCH 23:  An employee holds Banksy's 'Girl and Balloon' which was painted on an Ikea frame at Bonhams auctioneers on March 23, 2012 in London, England.  The painting, estimated at GBP 15,000 - 25,000, USD 24,000 - 40,000 and 18,000 - 29,000 euros, forms part of the Urban Art Sale, which takes place at Bonhams on March 29, 2012.  (Photo by Peter Macdiarmid/Getty Images)

see more

LONDON - OCTOBER 22: 'Balloon Girl' 2003 by artist Banksy is held by Bonham's Andrea Lee and is reflected in a mirror polished vase entiled 'B.O.O.P. by Ron Arad on October 22, 2007 in London. 11 paintings by graffiti artist Banksy are collected here for the first time for a sale called 'Vision 21' on October 24, 2007. (Photo by Peter Macdiarmid/Getty Images)

LONDON - OCTOBER 22: 'Balloon Girl' 2003 by artist Banksy is held by Bonham's Andrea Lee and is reflected in a mirror polished vase entiled 'B.O.O.P. by Ron Arad on October 22, 2007 in London. 11 paintings by graffiti artist Banksy are collected here for the first time for a sale called 'Vision 21' on October 24, 2007.  (Photo by Peter Macdiarmid/Getty Images)

see more

LONDON, ENGLAND - SEPTEMBER 16: A work by Banksy entitled 'Balloon Girl' is displayed at Bonhams Auction house on September 16, 2011 in London, England. The piece makes up part of the 'Urban Art' sale, and is expected to fetch between £20,000 -30,000 GBP when it goes on sale on September 21, 2001 at Bonhams Auction house in London. (Photo by Dan Kitwood/Getty Images)

LONDON, ENGLAND - SEPTEMBER 16:  A work by Banksy entitled 'Balloon Girl' is displayed at Bonhams Auction house on September 16, 2011 in London, England. The piece makes up part of the 'Urban Art' sale, and is expected to fetch between £20,000 -30,000 GBP when it goes on sale on September 21, 2001 at Bonhams Auction house in London.  (Photo by Dan Kitwood/Getty Images)

see more

LONDON, ENGLAND - SEPTEMBER 16: A Bonhams intern poses with a work by Banksy entitled 'Balloon Girl', at Bonhams Auction house on September 16, 2011 in London, England. The piece makes up part of the 'Urban Art' sale which takes place on September 21, 2001 at Bonhams Auction house in London. (Photo by Dan Kitwood/Getty Images)

LONDON, ENGLAND - SEPTEMBER 16:  A Bonhams intern poses with a work by Banksy entitled 'Balloon Girl', at Bonhams Auction house on September 16, 2011 in London, England. The piece makes up part of the 'Urban Art' sale which takes place on September 21, 2001 at Bonhams Auction house in London.  (Photo by Dan Kitwood/Getty Images)

see more

LONDON, ENGLAND - MARCH 23: A detail shows the reverse of Banksy's 'Girl and Balloon' which was painted on an Ikea frame on display at Bonhams auctioneers on March 23, 2012 in London, England. The painting, estimated at GBP 15,000 - 25,000, USD 24,000 - 40,000 and 18,000 - 29,000 euros, forms part of the Urban Art Sale, which takes place at Bonhams on March 29, 2012. (Photo by Peter Macdiarmid/Getty Images)

LONDON, ENGLAND - MARCH 23:  A detail shows the reverse of Banksy's 'Girl and Balloon' which was painted on an Ikea frame on display at Bonhams auctioneers on March 23, 2012 in London, England.  The painting, estimated at GBP 15,000 - 25,000, USD 24,000 - 40,000 and 18,000 - 29,000 euros, forms part of the Urban Art Sale, which takes place at Bonhams on March 29, 2012.  (Photo by Peter Macdiarmid/Getty Images)