When curators at the British Museum were approached in 2005 by an elderly man with a broad Lancashire accent asking for their opinion on a fragment of an Assyrian stone frieze that he said had been in his family since 1892, they had every reason to believe he was just the latest genuine enthusiast to seek their expertise.
Only when George Greenhalgh, an 84-year-old former technical drawing instructor from Bolton, hinted that the family would be willing to part with their prized artefact for £500,000 that the experts' concerns about the authenticity of 2,700-year-old art turned into full-blown suspicion.
On closer inspection, they noticed that the carving of a bearded horseman leading two steeds, supposedly part of a documented bas relief presented to the Assyrian monarch Sennacherib for his "palace without equal" in what is now Iraq, showed untypical harnesses and, crucially, a spelling mistake in the ancient Mesopotamian script. The frieze was in fact an extremely clever fake.
The museum contacted Scotland Yard's art and antiques unit, which in turn began an 18-month investigation into Greenhalgh, his 83-year-old wife, Olive, and their 47-year-old son Shaun, an antiques dealer . Its detectives, who are accustomed to dealing with the wide range of fraud afflicting the global art market, were astonished by what they found at the Greenhalghs' home. Their end-of-terrace council house contained a collection of phoney treasures, each painstakingly forged in original materials from Egyptian glass to Roman silver, along with detailed "histories" culled from obscure archaeological records and historical texts.
From a monumental Roman silver tray supposedly dug up in Derbyshire in the 1720s to paintings by L S Lowry to a sculpture by Barbara Hepworth, the family was responsible for a "cottage industry" producing at least 120 forged art works which, if they had all been sold at market rates, would have been worth £10m. Some items were so perfectly executed by Shaun Greenhalgh that they fooled experts at leading auction houses and museums.
Shaun Greenhalgh, the mastermind of the fraud, was sentenced at Bolton Crown Court yesterday to four years and eight months in prison, and his mother was given a suspended 12-month jail term after they admitted to conspiring to defraud museums and private collectors over 18 years.
George Greenhalgh, who is wheelchair-bound and suffers ill health, has pleaded guilty to conspiracy and will be sentenced after a medical report.
Detectives said the family was responsible for the "biggest and most diverse" production line of faked artworks the Yard unit has ever come across. The family made at least £850,000, although police believe the total may be nearer £2m.
Detective Constable Halina Racki, who helped co-ordinate the investigation, said: "They were some of the most unlikely people you would expect to be involved in something like this. They would produce an item, pretend it had been in the family for generations and ask for advice on its value or significance.
"If an institution or auction house expressed interest it might then suddenly become available for sale. But what is remarkable is the sheer breadth of what was produced. They went to great trouble to source the correct stone for faking Egyptian statues, and bought Roman silver to melt down into the Roman tray. Some of it is extremely well executed."
The son produced the artworks but left the selling to his father and, occasionally, his mother. Peter Cadwallader, for the prosecution, said: "His father fooled experts from all the great auction houses and other experts from Leeds to Vienna, from London to New York."
The fraud came to light only after British Museum experts spotted the Assyrian fake and began making inquiries about other items offered by the Greenhalghs or under Olive Greenhalgh's maiden name of Roscoe.
Five of the Greenhalgh forgeries
* The Amarna Princess
An alabaster statuette claimed to be from 1,350BC which the family sold to Bolton Museum in 2004 after it was authenticated by experts at the British Museum and Christie's. Bolton Council is trying to recover its money.
* The Risley Park Lanx
A heavy Roman silver tray which was dug up in a field in Derbyshire in 1729 and was believed to have been broken up and smelted down by farm workers. Shaun Greenhalgh produced a replica using Roman coins smelted in a small furnace kept on top of his fridge. The British Museum declined to buy it but two benefactors did and donated it to the museum.
* Barbara Hepworth "Goose", a clay sculpture, was sold to an offshoot of the Henry Moore Foundation in Leeds after George Greenhalgh pretended that his mother's uncle was curator of a prominent Leeds art gallery.
* Sketches by Thomas Moran
Shaun Greenhalgh boasted that he was so good at faking the work of the Bolton-born American artist left) that he could produce a forged painting by him in 30 minutes. Twenty-four fake sketches were sold in New York in 1995.
* Busts of Thomas Chatterton and John Adams
Bronze busts were made of the two men in a hired Bolton workshop. Shaun Greenhalgh may have been playing a private joke by focusing on Chatterton, who was a forger of pseudo-medieval poetry.
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