A man has been arrested in connection with the theft of treasures worth more than £1m from Arundel Castle.
The haul included a set of “irreplaceable” gold rosary beads that belong to Mary Queen of Scots.
A number of items were taken from the break-in at the castle in West Sussex on 21 May.
Staff were alerted at 10.30pm after a burglar alarm went off and police scrambled to the scene.
A 4×4 saloon car was later found burnt-out and abandoned.
Sussex Police said a 45-year-old man was arrested in Eckington, Worcestershire, on Tuesday morning in a joint operation with Gloucestershire Constabulary, West Mercia Police and Thames Valley Police.
He remains in custody for interview on suspicion of the burglary of the castle.
The stolen rosary beads were carried by Mary Queen of Scots to her execution in 1587.
Other items taken in the burglary included coronation cups given by Mary to the Earl Marshal, as well as gold and silver items.
Officers conducted eight warrants at addresses in Worcestershire, Gloucestershire and Oxfordshire and six other men were also arrested in connection with other offences, including alleged burglary, assault and drugs offences, all unrelated to the castle heist.
Detective Inspector Alan Pack, of Sussex Police, said: “Our investigation into the Arundel Castle burglary remains live and this action marks a significant step in our enquiries.
“I would encourage anyone with further information about this burglary to contact us and also remind people that the insurers have offered a substantial reward should any of the property be recovered intact.
“You can also contact us either online or by calling 101, quoting Operation Deuce.”
The collection, valued at more than £1m, comprised: Mary Queen of Scots’ rosary beads; seven gold/silver-gilt coronation cups (George II, George III, George IV, William IV, George V, George VI and Elizabeth II); a gold Earl Marshal’s baton; gold and enamel baton; other miscellaneous items including 10 silver-gilt apostle spoons, a silver-gilt casket with hunting and fishing scenes, and a silver-gilt mug.
Shortly after the break-in, a Sussex Police spokesman said: “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 at the time: “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.”
In June, Sussex Police released photos of two ladders used by thieves in the castle break-in.
The two metal ladders, one 6ft long and one 12ft long, but both capable of being extended to twice their lengths, had been used by the thieves to gain access to the dining room area where a window was forced to gain entry.
The well-used ladders had some worn labelling and the longer one had some distinctive black and yellow paint splashings.
Police hope someone in the decorating or building trade, or maybe someone who just had them at home, will realise they are missing, and will get in touch.
Watch: Mary Queen of Scots's gold rosary beads stolen in castle raid