The raiders parked their car and crossed the river Tweed in an inflatable dinghy before tracking across the rolling parkland of the castle, near Kelso, and drilling through an outside door in the east wing of the building.
Inside they smashed display cabinets in the public rooms and scooped up handfuls of valuables. Floors is one of Scotland's most successful tourist attractions, with more than 70,000 visitors last year.
The alarm system was activated during the raid, but the gang escaped back across the park and recrossed the river in the dinghy, which they then abandoned. The police set up roadblocks but there was no trace of the raiders.
The Duke, who was away on business at the time of the raid, said yesterday: 'It seems very probable the thieves came round beforehand posing as tourists. Sadly, it is all too easy for people to case the joint in houses like ours that are open to the public.' A member of his staff added: 'He is very shocked. The raiders were just barbarians. The mess is terrible . . . they smashed the cabinets and took the items on display by the handful.'Reuse content