CCTV footage of three burglars stealing an antique diamond tiara from a country estate has been released by police.
The trio are shown using “specialist diamond cutter-type tools” to steal the Portland Tiara from the Welbeck Estate, Nottinghamshire, on 20 November.
The helmet-wearing raiders are showered with sparks as they cut open an armoured glass case.
Detectives have appealed for information about the men and a silver Audi RS5 found burnt out nearby.
Burglars broke into The Portland Collection Gallery on the estate between 21:45 and 22:00 GMT.
Alarms were sounding at the time and a spokesman for the estate said security missed the men “by seconds”.
The silver Audi RS5 Quattro, registration KY61 USJ, was found burnt in Cross Lane, Blidworth, about 30 minutes after the burglary.
Det Insp Gayle Hart said police were keen to trace the vehicle’s movements, and further appealed for information about anyone who may have hired specialist power tools around the time of the raid.
The Duchess of Portland wore the tiara to the 1902 coronation of Edward VII.
Welbeck Abbey has been home to the Dukes of Portland since 1607.
The Portland Collection, housed in the estate’s converted gas works, is made up of paintings, jewellery and other art collected by the Dukes over 400 years.