If the Greenhalgh Collection had been assembled as one exhibition, it would have drawn critics from around the world.

Over the years, the Greenhalgh family amassed artworks from across four millennia. There were paintings by LS Lowry, a long-lost Barbara Hepworth sculpture, 19th-century American landscapes, a Thomas Jefferson bust, ancient Celtic jewellery, Roman silver plate and Assyrian reliefs dating from 700BC. The centrepiece was a 3,300-year-old statuette known as the Amarna Princess, made from Egyptian alabaster and depicting a daughter of the Pharaoh Akhenaten.

It had been authenticated by Egyptologists at the British Museum. But, like every other piece in this collection, it was a fake.

Each had been painted, carved, moulded or hewn in the Greenhalgh family’s council house in Bolton or in the garden shed. Many fooled the experts at salerooms and museums across Britain, Europe and America.

Three occupants of that house were convicted at Bolton Crown Court yesterday of selling faked and forged artworks between 1989 and 2006.

They are known to have presented 120 fakes to museums and auction houses with a potential face value of £10 million. They made at least £850,000 and, at the time of arrests, had more than £350,000 in the bank.

Shaun Greenhalgh, 46, admitted selling forged art and laundering the proceeds, specifically the money for the Amarna Princess. He was jailed for four years and eight months.

Olive Greenhalgh, 82, who came to court on crutches, admitted conspiracy to defraud and received a 12-month suspended sentence. The sentencing on wheelchair-bound George Greenhalgh, 84, a former technical drawing teacher, was deferred.

“They are possibly the most diverse forgery team in the world, ever,” said Detective Sergeant Vernon Rapley, of Scotland Yard’s arts and antiques unit.

Detective Constable Ian Lawson recalled: “There were blocks of stone, a furnace for melting silver on top of the fridge, half-finished and rejected sculptures, a watercolour under the bed, a cheque for £20,000 dated 1993 and a bust of an American president in the loft. I’d never seen anything like it.”

Working from sketches and old photographs, Shaun Greenhalgh invested in silver, stone, marble and other materials needed to recreate lost works. His particular skill was recreating Thomas Moran, a 19th-century American landscape painter.

The family sold dozens of Moran paintings and sketches at Bonhams in London and Sotheby’s in New York. The Greenhalghs tried the same ruse with a forged Lowry. It was found to be a fake, but the Greenhalghs sold it for £5,000 and it was sold on for increasing amounts. When police recovered it, the painting was on auction in Kent for £70,000.

The most ambitious fakes were offered with clever bogus history. The Amarna Princess statuette was apparently acquired at auction by a long-dead Greenhalgh great-grandfather.

Experts from the British Museum were extremely excited. The only comparable piece was in the Louvre in Paris. Bolton Museum bought it for £440,000. But when the Greenhalghs returned with the next haul from their great-grandfather’s forgotten collection, they aroused suspicion. This time an expert spotted flaws, and they were subsequently investigated.

What has never become clear is the family’s motivation. They had plenty of money but claimed welfare benefits and lived a far from lavish life with an old TV, battered sofas and a Ford Focus parked outside.

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