Historic heirlooms worth nearly £700,000 were stolen when thieves raided Goodwood House, near Chichester, on Thursday.
Sussex Police has made a nationwide appeal for information as to the whereabouts of the jewellery, which includes a diamond tiara and a ring that belonged to Charles II’s mistress.
The valuable items belong to Lord and Lady March, owners of the Goodwood Estate, and the couple say they have been left ‘devastated’ by the loss.
Detective Inspector Till Sanderson said: ‘The theft of these beautiful and treasured items have left the victims Lord and Lady March devastated at their loss.
‘An intruder broke into the house sometime after midnight on Wednesday and took thousands of pounds worth of jewels and watches, many of which are irreplaceable.
‘Forensic teams are working with detectives to investigate the circumstances and we are appealing for anyone who saw any suspicious activity during that night up until 7am or in the previous days to contact us.’
The historic items, with ‘huge’ sentimental value, include an 1820 diamond tiara, worth in the region of £400,000, and an antique diamond necklace from the first half of the 19th century, worth in the region of £200,000.
An emerald intaglio and diamond ring from 1800, engraved with the Duchess’s coronet and monogram CL for Louise de Keroualle, mistress of Charles II, was also targeted.