A £750,000 ring which reportedly went missing from the British Museum six years ago has only recently been registered as lost.
The piece of jewellery formed part of the museum's heritage asset collection but was first reported absent in 2011.
Details of the loss were not made public at the time and have come to light only with the publication of accounts from the Department for Digital, Culture, Media and Sport.
"During the year, a ring from the British Museum's heritage asset collection valued at £750k was declared lost under the British Museum's Procedure for the Reporting of Unlocated and Lost Objects," the entry in page 94 of the 253-page document said.
The Daily Mail said the piece was a Cartier diamond ring, given to the museum by an anonymous donor.
A spokeswoman for the British Museum told the paper: "The ring was found missing from its proper location by British Museum staff in August 2011.
"British Museum procedure, as agreed by trustees, requires the ring formally to be reported as lost five years after the initial discovery of its absence.
"The museum takes the security of the collection extremely seriously. The museum has since reviewed its security and collections management procedures and dedicated significant investment to improved security across the estate."