A rare 18th century Cullen Stone linked to Wolstonbury Hill was among the five millstones taken from one of Clayton’s iconic windmills.
Volunteers believe thieves needed heavy lifting gear and a lorry to steal five millstones from the grounds of Jill windmill.
The stones are at least 100 years old and were stolen towards the end of last week.
Simon Potter, a trustee and founder member of the Jack And Jill Windmills Society, said: “We came up here on Saturday and discovered the theft. The millstones weigh about half to three-quarters of a ton each. They must have needed three or four blokes and a lorry to move them.
“They’ve either been stolen to order for a garden water feature or possibly for architectural salvage. It’s so sad because we’re a charity and most of the stones were donated.
“Two of the millstones came from the water mill at Goddards Green, two from Plumpton water mill and one is a rare ‘Cullen’ stone’ that was used originally for crushing lime at the bottom of Wolstonbury Hill. They sell on Ebay for various amounts but to us they are priceless.”
Cullen stones were imported from Cologne in Germany in the 18th century and the one that was stolen bears the date 1721 or possibly 1731 on the back with the letters ‘O’ and ‘ie’. It is a distinctive dark, grey volcanic lava stone.
“The millstones were in the grounds and not inside the mill. A commemorative millennium plaque had been attached to one of the stolen millstones and that was un-screwed and left behind.
Simon said: “They left two millstones in the grounds – one was resting on pallets and the other one was too heavy for anyone to lift. We think they stole the millstones in daylight and people walking past probably thought they were workmen or volunteers.”
The thieves managed to get the gate to Jill’s grounds open without removing the padlock, possibly by lifting it up from its frame. Fencing belonging to Mid Sussex District Council was damaged in the raid and will have to be repaired.
A Sussex Police spokesman said: “Each stone is about four foot across. One is a distinctive dark grey lava stone, another is a standard millstone but with four holes drilled into it.
“At least four people would probably have been needed to move each stone and a hedge was cut to enable them to drive them away.
“We would appeal to anyone who saw any suspicious activity, has any information or has been offered these stones to contact police on 101 or the independent charity Crimestoppers anonymously on 0800 555 111.”