Banksy, the self-styled urban guerilla graffiti painter, is not an authentic artist, according to ‘Rat Poison’, a new body set up to police the ever-expanding boundaries of the art market.

Rat Poison is the latest in a lengthening list of 500 verification boards set up over the past year to authenticate works by the UK ’s most dismal and untalented stencil painter. Other bodies include Vermin, Pest Control, DynaPlod, Let Us Spray, CrapTrap, Wanksy, and Waste Disposal Skip.

“Banksy is not an artist,” said Rat Poison CEO Marguerita Pizza. "He’s a plonker and an ingrate. People like him will be forgotten in a few years. He can’t compare with Masaccio. Now there’s a wall painter. Shit, that guy could paint a wall! Have you seen that Brancacci Chapel he did? Now that’s what I call urban art. Ohmygod, the way he climbed up there on that scaffold in the dead of night and worked his fingers to the bone with only a bottle of…”

At this point a team of white-coated mental health operatives led by former Met Chief Sir Tony Blair closed in on Ms Pizza and bundled her into the back of a white van which only a few moments earlier had been spray-painted by Banksy with a perfect reproduction of Paolo Uccello’s Battle of San Romano.

Christie’s Urban Art expert, Mr Juicy Pickledonion, 23, declined to comment. He was said to be sitting on his window ledge five storeys up, a copy of Christie's balance sheet quivering in his hand as the markets tumbled. 

Lionel Turnbull