An octogenarian and her son were jailed today after perpetrating an £850,000 conspiracy to defraud art institutions with fake antiquities and artworks produced in their Bolton council house and garden shed.

Olive Greenhalgh, 82, received a 12 month sentence suspended for two years for her role in the scam, while her son Shaun Greenhalgh, 47, was jailed for four years and eight months.

Mrs Greenhalgh’s husband George, 84, who attended Bolton Crown Court in a wheelchair, will be sentenced at a later date over his involvement in the fraud to give the judge time to consider whether his frail condition would allow him to serve a custodial sentence.

In what Judge Morris described as an “ambitious conspiracy” conducted with no resources, the family operated a major cottage industry from their three bedroom home, producing up to 120 fakes including Henry Moore statues, Roman plates and copies of paintings by LS Lowry.

In their greatest coup, Shaun Greenhalgh “knocked up” a fake Egyptian statue in just three weeks in his garden shed, a piece which, astonishingly, was authenticated by the British Museum and valued by the Egyptology Department at Christie’s at £500,000. The Princess Amarna statuette was snapped up by Bolton Museum for the sum of £440,000 in 2002 and displayed until the plot was uncovered in 2006.

The court heard that the mastermind behind the forgeries was Shaun Greenhalgh, who displayed remarkable artistic talent. However his elderly parents also played crucial roles in establishing fraudulent histories for the pieces and selling them to galleries and collectors.

George Greenhalgh, a former technical drawing teacher, was the frontman who would turn up in his wheelchair to ask experts to identify his “discoveries”, while his wife once claimed a forged LS Lowry had been given to her as a 21st birthday present by her father.

Detective Constable Ian Lawson, of Scotland Yard’s arts and antiques unit, said Shaun Greenhalgh was not motivated by greed, but by a desire to embarrass the art world. Despite their profits being estimated by the judge at £850,000, the court heard that they continued to live a basic lifestyle.

He said: “He thought he was having it over a lot of people that should have known better. It is more of a resentment of the art world - to prove that they could do it.”

After his arrest the creator boasted to detectives that he could produce Thomas Moran landscape, worth up to £10,000, in just 30 minutes.

Other British artists he imitated included Samuel Peploe and the sculptor Barbara Hepworth.

The family also created astonishingly convincing works that purported to be thousands of years old, but it was this aspect of the venture that ultimately led to their downfall.

The Greenhalghs had already sold one Roman plate to the British Museum as an 18th or 19th century replica, but when they turned up with three Assyrian reliefs in 2005, the museum’s experts were unconvinced. After spotting a spelling mistake in the text and noticing that ancient horses were wearing modern equipment, the police were called in and their plot began to unravel.

When the family home was searched in March 2006, detectives were stunned to discover that the modest home concealed an elaborate forgery factory well-stocked with raw materials such as Roman glass and silver coins. Watercolours were hidden in wardrobes, half-finished statues dotted the kitchen and a furnace for melting precious metals was on top of the fridge.

Detective Sergeant Vernon Rapley said it was possible that the full extent of the family’s prodigious output had yet to be uncovered, because as many as 100 forged pieces could still be in circulation.

Expressing detectives’ shock at the audacity of the plot, he added: “It does show a real skill with no resources and no real facilities behind you to produce things like this.”

Outside court, Stephanie Crossley, assistant director of adult services at Bolton council, said the whole incident had been “regrettable but the council carefully followed established practice in the purchase of the statue”.

She said: “We welcome the judge’s comments. He said that we were victims of the ’most clever deception’. The museum did not rely on its own judgment. He said that he could see no criticism of Bolton Museum in what it had done and no criticism of any individual.

“Our staff acted entirely correctly following best practice and procedures as laid down in the Museums, Libraries and Archives Council guidelines and the statue was evaluated in accordance with museum practice and the demands of the funding bodies."

It is understood a confiscation and forfeiture hearing related to the case will take place at Bolton Crown Court on January 25 next year.

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