An old box truck covered in graffiti by anonymous street artist Banksy is expected to fetch up to $2 million when it goes under the hammer this weekend.

Titled Turbo Zone Truck (Laugh Now but One Day We’ll Be in Charge), the 1988 Volvo FL6 box truck was once used by a travelling circus in the early 2000s.

It has a painted surface area of 80 square metres, making it Banksy’s largest piece of work.

The vehicle is expected to rake in between $1.3 million and $2 million when it rolls onto the auction block on September 14 at the Bonhams Goodwood Revival motor festival in the UK.

Auctioneer Bonhams said the co-founder of the Turbozone International Circus offered the truck to Banksy as a canvas in 1999 before it was driven to travelling performances around Europe and South America over several years.

At the time of painting, Banksy’s unique brand of anarchist political activism was relatively unknown.

Today, his distinctive stencilling and dark humour is recognised around the world.

The designs on the truck feature a group of soldiers running away from a cannon in front of a background of flying monkeys and red stars, accompanied by a silhouette of a man swinging a hammer at a TV set sitting atop metal cogs.

Bonhams said the designs served as a “fascinating record of how the artist’s calls for anarchy and social change were already central to his work”.

The truck is featured in Banksy’s 2005 book Wall and Piece.

Bonhams’ global head of post-war and contemporary art, Ralph Taylor, said the mysterious artist was “arguably the most important artist to have emerged since the millennium”.

“This, his largest commercial work, represents a new high watermark of quality for works of his to appear at auction,” Mr Taylor said.

To this day, the true identity of Banksy is unknown, though it is widely believed he is from Bristol in the UK.