A Ford Focus driver could have given up more than a £10 note when he paid to have his car washed recently, the Liverpool Echo reports.
Staff at Five Star Wash in Liverpool firstly thought they had been given a fake note by the mystery motorist.
However, on closer inspection it was realised that the note may have been a piece of work by controversial street artist Banksy.
The banknote replaces the head of the Queen with Princess Diana and also bears the words "Banksy of England".
A similar banknote is currently up for sale on the website eBay for almost £20,000.
Manager of the car wash Edward Humphry told the publication: "He gave us the note and said ‘keep the change, it’s worth more than that’.
"He wasn’t a scally trying to drive off with a free car wash."
Banksy uses a distinctive stencilling technique in his artwork and once recreated the scene from Pulp Fiction, but with Samuel L Jackson and John Travolta holding up bananas instead of guns.