Geoffrey Harkin, 58, of Wakefield, North Yorkshire pleaded guilty to the theft of an important collection of Sèvres porcelain at Firle Place near Lewes in July 2009, a £27,000 raid on Longnor Hall in Shropshire and the attempted sale of a £200,000 table clock by Thomas Tompion stolen from Levens Hall, near Kendal in Cumbria in September 2009.
The Tompion, for which a reward of £20,000 was later advertised, was the item which would lead to his arrest.
Carlisle Crown Court heard that, although Harkins did not actually commit the Levens burglary himself, he had 'cased the joint' four days previously after joining a lunchtime tour of the house. A bronze and ivory figure of Napoleon on horseback by E.B. Masson was also stolen in the burglary.
Six months later, he contacted Levens Hall's owner Hal Bagot claiming he could recover the clock for £25,000 and arranged a 'no questions asked' exchange at Birch Services on the M62 near Rochdale.
Expecting to meet Mr Bagot, instead he was met by undercover officer DC Steve User of Cumbria Police who found the 17th century table clock in the boot of his BMW and confiscated both a mobile phone and a National Trust membership card - "an essential bit of kit for a country house burglar" said the prosecution.
Data from the phone placed Harkin at the location of the burglaries at the time they were committed while CCTV found footage of him on guided tours of the targeted houses in the weeks before the thefts.
On March 25, Judge Peter Hughes told Harkin: "You selected your targets by posing as a member of the public. You were, to put it colloquially, casing the joint. You were either stealing to order or you had a good knowledge of what was valuable and worth stealing."
He gave Harkin concurrent sentences of nine years for the Firle Place burglary, seven years for the Longnor Hall burglary and five years for handling the Tompion clock. In the light of the prosecution, two other charges - burgling a National Trust property in Cornwall and stealing a £50,000 sundial from Dalemain House, near Penrith - were left lying on the court file. The court was told he had 18 previous convictions, mainly for theft.
Harkin is understood to have passed on some of the items to an associate, Gary Swindell, 58, of Bradford, who was given a three-year sentence for handling stolen goods - some of which were sold at a car boot fair in York.
With the exception of the clock, none of the items stolen have been recovered.