Raiders at a Midland tourist spot hot-wired a crane before loading copper sheets worth about £70,000 in a “pre-planned and highly professional” attack.

Thieves disabled an alarm and clambered through an air vent at Severn Valley Railway before starting up a overhead gantry crane and then using it to lift copper sheets into a waiting lorry they had reversed into Bridgnorth Boiler Works.

The sheets, weighing an estimated six tons in total, were replacement sections for the fireboxes of several locomotives.

Bosses fear the theft was prompted by soaring copper prices and today launched a £5,000 reward for information leading to the recovery of the copper, stolen on the night of January 20.

Thieves had made an unsuccessful attempt to break into the boiler shop before returning on the same night and used two ladders — one propped on top of another — to smash the security alarm 16ft up on the outside wall of the building.

They broke down the reinforced air vent grille to gain access to the works.

The gang also stole a steam pipe from another locomotive and took the chains from the gantry crane.

Scene of crime officers from West Mercia Police have been studying scrapes on the wall of the boiler shop thought to have been caused by a vehicle, and footprints in the dust on the floor.

The theft, believed to have taken place some time after midnight, was discovered by SVR loco driver Bob Toy at around 7.30am last Friday.

Railway general manager Nick Ralls today described the attack as pre-planned and highly professional.

He added: “It’s sickening — a kick in the guts.

“This wasn’t an opportunist crime.

“Just like everyone else in business though, we’re feeling the pinch of recession, and these are hard times for everyone. We didn’t need this.”

Contracts manager Duncan Ballard added: “Copper prices are at, or near to, a record high, and heritage railways are being seen as easy targets by scrap metal thieves.

“We’re only the latest in a long line of railways and railway workshops to be hit.”