Works of art stolen from a 17th-century manor house were worth an estimated $142 million, making the raid the largest property theft in British history, according to reports.
Thieves driving Jeeps forced entry to the estate of property tycoon Harry Hyams in February, stealing around 300 museum-grade artifacts, police said.
Officers said they initially estimated the goods, including paintings, clocks and silver, were worth about $36 million.
However, The Art Newspaper, based in London and New York, reported Sunday that a new assessment by police and insurance companies values the items at four times that figure.
It would mean that the value of the theft from Ramsbury Manor, at Ramsbury in southern England, is larger than the $92 million stolen in Britain's largest cash robbery earlier this year.
Wiltshire Police, investigating the theft, refused to comment Monday.
"Though it is difficult to put precise figures on works of this type, these items were of the very highest quality, the like of which have seen their value increase by tens if not hundreds of percent over the last few years," Julian Radcliffe, chairman of the Art Loss Register, the London-based international art recovery specialist, told The Associated Press.
Hyams, 78, amassed his fortune in real estate and was ranked 204th in a 2006 Times newspaper survey of Britain's richest people.