Banksy's SWAT Van artwork comes to auction at Bonhams on June 29.
The unique piece has remained unseen since appearing at the street artist's debut American exhibition in Los Angeles in 2006.
This van and a live elephant were the stars of Banksy's debut US exhibition
Depicting a small boy outwitting a group of Special Forces soldiers with an inflated paper bag, SWAT Van is a fine example of the Bristol, UK artist's humorous anti-establishmentism.
It is estimated at up to £300,000 ($443,000), far below the $1.7m record for a Banksy, set by Keep It Spotless in 2008.
It has been declared genuine by Banksy's authorisation service, Pest Control Office, a fact that will offer encouragement to reticent bidders to put up their hands.
Ralph Taylor, Bonhams' senior director of post-war and contemporary art, commented: "All of Banksy is on show here: his bravado, his imagination, his technical prowess, his confidence and his willingness to put his head above the parapet and use truth as a weapon."
Banksy's first solo show in the US, titled Barely Legal, was typical of the artist. In addition to the van, it featured a multi-coloured elephant, which walked around the gallery. Visitors were instructed not to discuss "the elephant in the room".
Relatively unknown in the US previously, Barely Legal brought Banksy to the attention of the American masses, and Brad Pitt and Angelina Jolie were among the guests at its opening night.
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