A gang of 14 "extremely violent" criminals have been arrested in connection with a 21 month spree of raids on Britain's stately homes.

More than 100 officers from five different police forces made the arrests in Oxfordshire, Worcestershire and Gloucestershire yesterday as part of the investigation into the crimes.

The detainees are being questioned about 23 raids, including some of the highest profile burglaries the country has ever seen, which are believed to have netted up to £30m worth of goods.

One of the addresses targeted by the gang was Ramsbury Manor in Wiltshire, a £21 million mansion belonging to 77-year-old property tycoon Harry Hyams.

Millions of pounds worth of antiques and fine art, described at the time as being of "great rarity and of museum quality", were stolen from the 17th century manor house during the raid in February 2005.

Thieves stole hundreds of items including porcelain, silver, clocks, barometers, and paintings from the property, believed to be one of Britain's most expensive private homes. Other properties raided included Ombersley Court in Worcester, Spetchley Park in Worcester (pictured), Woolley Park House in Berkshire, Stanton Harcourt Manor in Oxfordshire and Rendcombe Manor in Gloucestershire.

The gang also hit ATM machines, businesses and stores during their year and a half spree and so far only £10 million worth of goods have been recovered.

Their first hit is believed to be on an ATM machine on the M5 in December 2004 and the gang's last raid was on Woolley Park House in April 2006.

They were caught as part of Operation Haul which was established in October 2005 and brought together Thames Valley Police, West Mercia Constabulary, Warwickshire Police, Wiltshire Police and Gloucestershire Police.

Seven people were arrested during the early morning raids in Cleeve Prior, Evesham, six were arrested in Gloucestershire and one in Oxfordshire.

Thames Valley police Assistant Chief Constable Francis Habgood said yesterday: "The crime being investigated by Operation Haul include some of the highest profile and highest value burglaries this country has ever seen."

She added: "These arrests should demonstrate that where criminality does not recognise police force boundaries, neither do we - we will work together very closely to ensure that suspects are identified and brought to justice."

Assistant Police Constable Mark Polin of Gloucestershire Police added: "These people had the potential to act in an extremely violent way to achieve their goals."

And Detective Superintendent Mark Warwick, from Thames Valley police, said that £30m was a conservative estimate on the value of goods stolen.

"We believe a great deal has been sold on, we have recovered a significant amount but a great deal is still outstanding, we will be speaking to a number of people over the next few days," he said.

"In terms of the scale, this is a significant operation for the five forces, £30 million is probably an underestimate.

"We will work together to ensure these criminals are brought to justice."

Police have recovered around half of the antiques that were stolen from Ramsbury Manor.

Items stolen during the raid included a 1675 clock from the reign of King Charles II and a Matthew Boulton candelabra.

The haul was estimated by police at the time to be worth "several million pounds", although one unofficial estimate put the figure as high as £30m, which would make it one of Britain's biggest domestic burglaries.