Imports ceased during the conflict, provoking domestic cobalt operations to spring up in the UK, though the industry collapsed soon after imports resumed.

"This discovery is helping us understand a less well-known chapter in the story of mining at Alderley Edge, which has been explored and exploited for 4,000 years," said Jamie Lund, who is a National Trust archaeologist.

Cavers have accessed portions of the vast network of tunnels, and the National Trust has used 3D scanning technology to plot inaccessible areas.

Lund said that all discovered objects have been photographed and documented, and will remain in the mine in the underground conditions that have preserved them so well.

"It leaves the mine as a time capsule, protecting a place that was once a hive of activity for future generations to explore and enjoy," said Lund.