Museum's £1.7m whip-round fails to save its Roman mask

Nearly two thousand years after it was entombed in the soil of a Cumbrian field, and five months since it dazzled the world when it was unearthed by two men with a metal detector, a mesmerising Roman mask was sold in just three minutes yesterday – leaving a mystery bidder with a gem on his hands and a community in tears.

The bronze cavalry parade helmet, dating from the late first century or early second century, was auctioned in London for £2,281,250 – about eight times its expected price – to an anonymous telephone buyer.

The sale was a crushing disappointment for staff at Tullie House Museum in Carlisle, who had spent weeks trying to raise enough money to keep the artefact in Cumbria for public display. They had funds to stay in the bidding until it reached £1.7m – a staggering sum for a provincial museum – but it was not enough.

Campaigners had hoped that having the Crosby Garrett Helmet, named after the village near which it was found, on show would draw thousands of visitors to a part of the country that relies heavily on tourism. Their only hope now is that the Government will place an export ban on the mask, giving the museum time to raise the extra cash to match the sale price.

The bronze helmet, described by experts as "an extraordinary example of Roman metalwork at its zenith", would not have been worn in combat but kept for parades and festivals. Only three of its kind have ever been found complete in Britain. The Ribchester Helmet was uncovered in 1796 and is in the British Museum. The Newstead Helmet, found in about 1905, is displayed in the Museum of Antiquities in Edinburgh.

The guide price for the Crosby Garrett Helmet, which is considered superior to the other two, was between £200,000 and £300,000. But when it went on sale at Christie's, in South Kensington, six bidders entered the fray – two in the room, three by phone and one via internet from California – and swiftly pushed up the price. It is thought the buyer may be from overseas. The bidder from California, believed to be representing the Getty Museum, dropped out at £800,000.

The helmet was unearthed in May by an unnamed father and son, from Peterlee, Co Durham. They had spent years running their metal detectors over a site near Crosby Garrett. Their earlier searches turned up nothing of any value but they carried on because they liked the view. When they saw the helmet lying face down in clay, they thought it was simply a Victorian ornament.

Because the helmet was made of bronze, and did not form part of a large haul, their extraordinary find did not qualify in law as treasure, so they could have sold it without reporting to the Portable Antiquities Scheme (PAS), which protects valuable archaeological finds. They chose to do so voluntarily, however.

Tullie House Museum ran a fund-raising drive in the hope of buying the helmet. Thousands of people contributed, including children who emptied their piggy banks. The museum had already secured £1m from the National Heritage Memorial Fund and a further award from the Art Fund.

Stephen Deuchar, director of the Art Fund, said: "It is a great shame that, so close to the mark and with such great public support, Tullie House has been unable to secure the Roman helmet. We now hope that the export system will be able to kick in to action, allowing the museum another opportunity to acquire this remarkable work."

"It's so annoying," said Sally Worrell, of the PAS. "I'm gutted. It is frustrating to have worked so long on this and then not see it go to the museum."

Georgiana Aitken, the head of antiquities at Christie's, said: "This is an exceptional object – an extraordinary and haunting face from the past – and it has captured the imagination of everyone who has come to admire it."