A set of gold rosary
ติดตั้ง slotxo beads carried by Mary Queen of Scots at her execution in 1587 has been stolen along with more than £ 1m of gold and silver items in a raid on Arundel Castle.
The artefacts were snatched from the West Sussex castle on Friday night.
Other pieces taken during the raid include coronation cups given by Mary to the Earl Marshal.
An Arundel Castle spokesman said the stolen items were of "priceless historical importance".
The castle only reopened to the public on Tuesday.
Staff were alerted to the break-in at 22:30 BST on Friday after a burglar alarm went off.
Sussex Police told the BBC the thieves entered through a window and smashed a glass cabinet to grab the items.
Det Cons Molly O'Malley said the force believed a 4x4 saloon found abandoned and on fire in nearby Barlavington "was linked".
'Unique artefacts'
The castle spokesman said: "Various items have been stolen of great historical significance.
"The rosary is of little intrinsic value as metal, but as a piece of the Howard family history and the nation's heritage it is irreplaceable."
A spokesman for Arundel Castle Trustees said: "The stolen items have significant monetary value, but as unique artefacts of the Duke of Norfolk's collection have immeasurably greater and priceless historical importance.
"We therefore urge anyone with information to come forward to the police to assist them in returning these treasures back where they belong."
Brighton & Hove Archaeological Society tweeted: "What terrible news from Arundel. This theft is from all of us. It is our heritage."