METAL thieves have stolen a unique relic of West Somerset's industrial past.

A cast iron crank dating from the 1850s has been taken from the West Somerset Mineral Railway on the Brendon Hills.

The crank, which weighed more than half a ton and measured just under five feet in length, disappeared from the Langham Hill engine site earlier this month.

Phil Gannon, a member of the West Somerset Mineral Line Association who gives guided tours around the site, said it had been there on September 7 when he took a party of visitors around but was not there when he went back ten days ago.

"It's heartbreaking - this was one of the best artefacts to be found on the site," he said.

The crank, which once would have been a vital part of the beam engine that operated between 1866 and 1878, had lain buried in the ground for more than a century before it was uncovered during excavation work in the mid 1990s.

Conservation work to preserve it was carried out in 2007 with the help of Heritage Lottery funding.

"As scrap metal, it will have nominal value but its historic value cannot be measured," said Mr Gannon.

"It is a great loss that visitors and future generations will be denied the chance to view and experience one of the few tangible remains of this former Victorian enterprise."

Mr Gannon said the site had been targeted again within the last few days.

"A reel of original cable used to support an aerial rope-way has been chopped into small lengths," he said.

"Luckily it hasn't actually been removed but it looks as though someone had been getting it ready to take it off the site.

"They must have come up with a powered angle grinder.

"It's such a remote area but we would just ask everyone to keep an eye out for any suspicious activity."

Mr Gannon said the theft of the crank and the damage to the cable had been reported to the police and anyone with information should contact local officers, the Exmoor National park Authority or the Forestry Commission on 01278 732319 which owns the land.

The 11-mile long mineral line railway was constructed between 1857 and 1864 to transport iron ore from the Brendon Hills to the harbour at Watchet for shipment to smelting works in South Wales.