"Our heritage is being trampled on ... I think it is rather extraordinary. I would hope it is extraordinary and exceptional," Associate Prof Mark Stocker said yesterday.
He is one of a small team of New Zealand museum curators and academics who have played detective for more than a year to piece together a global artefacts puzzle.
The artefacts - a small bronze statue of the founder of Canterbury, John Robert Godley, a carved Maori pare or lintel dating from about 1880, a carved Maori panel and a small model of a carved Maori dwelling or pataka - were all donated to a British museum which closed in 2002. That institution passed on its collection of more than 11,000 items to the British Empire and Commonwealth Museum (BECM) in Bristol.
An academic with 30 years' experience and an authority on Victorian statues, Prof Stocker became involved in late 2009, when he was asked by the Christchurch Art Gallery for advice on the whether the gallery should buy a Godley statuette on sale in a London antique shop for 35,000.
After consulting books and talking to other specialists, he confirmed the statuette had been part of the BECM collection. The panel, pare and pataka, also in the shop, were also traced to the museum collection and were returned.
However, more detective work uncovered the pare and the pataka about to be auctioned at Auckland art dealership Dunbar Sloane in September last year.
Prof Stocker sought legal advice and informed the New Zealand Police.
The pataka was withdrawn from sale, but the lintel was auctioned and sold to a private buyer.
He said the items reaching the open market raised serious questions about how safe historical treasures entrusted to museum collections could ever be.
There were three possibilities about how the items came to be for sale, he said. Someone may have stolen them to make money, they may have been sold by accident, or they may have been sold with permission.
The London antique dealer said he bought about 150 items for 115,000 and received receipts signed by BECM director Gareth Griffiths. British newspapers have reported trustees of the museum as saying Dr Griffiths has been dismissed, although he disputed that.
The BECM trust board, headed by Sir Neil Cossons, internationally respected heritage adviser and a frequent visitor to Dunedin, is auditing the collection to see what items are missing. Sir Neil said the board had authorised the sale of some low value items.
The British police are also investigating. There was no way of knowing how many items had already been sold or were on the market, Prof Stocker said.
"Is this the tip of the iceberg? I really, really can't answer that. There has been talk of a carved rhinoceros horn worth tens of thousands of dollars, and an important North American landscape painting from the 19th century."
Publicity about the four New Zealand items would probably result in curators and art historians keeping a closer eye on sales and antique shops, he said.
While there was little a museum could do if someone sold items without permission, Prof Stocker said he believed all museums should take care when selling items and follow "due process".
It was important to consider the original donors and ensure "maximum transparency and publicity" about which items might be sold and why.
"Institutions should lean over backwards to be honest, genuine and ethical about it."
He was particularly offended about the intended sale of Maori artefacts, which he said did not respect the technical and spiritual qualities Maori artists brought to their works.