Members of an organised crime gang are beginning prison terms after plotting to steal up to £57million in rhino horn and Chinese artefacts in a series of museum raids.
The group, dubbed the Rathkeale Rovers because of their links to the Irish town, targeted high-value objects in a string of break-ins, including Durham's Oriental Museum and Cambridge's Fitzwilliam Museum in 2012.
Judge Murray Creed heard that although the items stolen in Durham and Cambridge were valued at around £17million, detectives believe they might have fetched more than three times that figure on the booming Chinese auction market.
Members of the same gang also masterminded an offence at Gorringes Auction House in Lewes, East Sussex, and organised the disposal of stolen artefacts in what the judge said was "an extremely sophisticated conspiracy".
Sentencing seven of the 14-strong gang, Judge Creed said the criminal enterprise "involved very high value goods with significant harm caused to victims, both museums and members of the public who would otherwise have viewed the material stolen".
He added: "It is a conspiracy both sophisticated, skilled and persistent, involved significant cultural loss to the UK of museum quality artefacts and items from international collections."
In all, 13 men are being sentenced following three trials which concluded with the gang and its associates convicted of wide-ranging criminal conspiracy to steal, which uncovered connections to Ireland, Europe and China.
The judge began by jailing Richard "Kerry" O'Brien Jr, 31, of Cambridgeshire - also of Rathkeale in the Irish Republic for five-and-a-half years.
His uncle, John "Cash" O'Brien, aged 68, of Fifth Avenue in Wolverhampton in the West Midlands was jailed for five years and three months.
Also in the dock was Daniel "Turkey" O'Brien, 45, and Daniel Flynn, also 45, both of Orchard Drive, Smithy Fen, Cottenham, Cambridgeshire, who were jailed for six years and eight months and four years, respectively.
The judge said he had found Flynn to have played "a leading role", but reduced the man's sentence based on "the fragility of his mental health".
Alongside the men in the dock was 56-year-old Donald Wong, of Clapham Common South Side in Lambeth, London, described by the judge as "a buyer, seller and valuer". He was jailed for five-and-a-half years.
Paul Pammen, aged 49, of Alton Gardens in Southend-on-Sea and 37-year-old Alan Clarke, of Melbourne Road in Newham, London, who was said to have headed the gang's "disposal team", were also both jailed for five-and-a-half years each.
Six other men convicted over the conspiracy will be sentenced tomorrow.
A 14th man had already been convicted and sentenced for his part in the crime, last year.
The judge said the operation to "plunder" rhino horn, carved horn and carved jade items started off "small-scale" in January 2012, but that after initial failures and botched thefts - in one case the burglars forgot where they had hidden their haul - "planning paid off".
"It was serious organised crime," he added.
In their most successful theft 18 pieces of Chinese jade were stolen from the Fitzwilliam Museum and although experts provided various valuations up to almost £18 million the judge described them as "priceless".
He added: "They were part of a national collection split between the museum in Cambridge and the British Museum in London."
Afterwards, that haul was stored in a safe house, being taken by taxi to Purfleet in Essex where they were spirited away.
The judge continued: "The conspiracy spanned England, Scotland, Northern Ireland and the Irish Republic, references were made to France - the Cherbourg visit, Hong Kong and also the United States and Germany, also featured in the evidence the court heard over the three trials."
He said the gang had either stolen or tried to steal "highly prized museum-quality" items, often with historic Imperial Chinese dynastic connections, with the exception of an attempted theft on an auction house in March 2012 in which the bungling thieves took the wrong item.
On two occasions the Oriental Museum in Durham was targeted, but also the Castle Museum in Norwich, Gorringes Auction House in Lewes East Sussex, and the Fitzwilliam Museum.
The men carried out reconnaissance of these and other sites, including three museums in Glasgow, and another auction house in Yorkshire.
Mr Creed said there had been "no expression of regret or remorse" from the men, and acknowledged there was "no prospect of recovery".