With his knack for provocative, headline-grabbing stunts, Banksy is rarely far from intrigue.
Now the enigmatic artist is at the centre of one of the more puzzling riddles of his colourful career, just days after his painting Devolved Parliament sold for a record £9.9 million at auction.
No sooner had Sotheby's hammer come down on the work – which shows a House of Commons packed with chimpanzees – than questions began to swirl around the art world as to whether Banksy actually created it.
Certainly, the realistic style and high level of technical sophistication are very different from the graffiti art for which he is known.
Instead, it has been suggested the work is really the creation of another artist, Mason Storm.
Storm has painted realistic-looking chimpanzees before and – like Banksy – keeps his real identity secret, always wearing a balaclava in public.
The debate began with an essay that artist Paul Kneen posted on the website of his gallery, Creative Folk.
He wrote: 'To me it's a masterpiece. But nobody seems to have picked up on the idea that actually this is nothing like anything Banksy has produced before.'
And he suggested the mysterious Storm might be the real artist.
One art fan posted images of monkeys by the two artists side-by-side on Twitter, writing: 'Fine art v stencil art. You sure Devolved Parliament is Banksy? I don't think so.'
Storm first acquired notoriety a decade ago when he threatened to paint a portrait revealing Bansky's identity.
Contacted by the MoS about the chimp controversy, he replied mischievously: 'I have never heard of Banksy.
'Banksy has never heard of me either, apart from the quote he said about me: 'Mason Storm? A desperate cry for art attention.'
'My paintings sell for around five grand. Monkey Parliament sold for ten million, so therefore it can't possibly be one of mine.
'I will however say that whoever painted it is an exceptionally talented painter. A genius, for sure.'
Originally entitled Question Time, the 13ft-long painting was first exhibited in 2009.
Art critic David Lee also voiced his doubts, saying: 'It's probably too finely worked to be by Banksy.
'It's hardly unusual for artists who can't paint 'properly' to commission someone else to do it for them. But does it matter if it isn't painted by Banksy? Of course not.
'With Banksy we are dealing with a sloganiser, not a technician.'
But artist Charles Thomson said: 'To say an oil painting on canvas is not by Banksy because it is not a spray painting on a wall is like saying spot paintings can't be by Damien Hirst because they are not a dead shark in a tank.
'It is nonsense.'
Sotheby's said the work had been examined by experts and added: 'There is no evidence to suggest it is not by Banksy: it is signed and dated by the artist, and accompanied by a certificate of authenticity.'
A spokesman for Banksy declined to comment but he has posted on Instagram: 'I made this ten years ago... Shame I didn't still own it.'