Nigel Smith, director of Claude N Smith roofers, has decided to re-open a mine on his land in Northampton to start extracting Collyweston stone to split into roofing slates.

Nigel’s father, Claude, who started the firm, bought the land that the mine is on in the 1980s when he needed space to expand. The mine had then been shut for many years and there was little incentive to re-open it because there was plenty of reclaimed Collyweston to be found. Now it is in shorter supply.

Collyweston is produced by leaving the logs of stone in the open during winter frosts, so the frosts split it. But the winters are seldom cold enough to split the logs these days, so Nigel has bought a 40ft (12m) refrigerated lorry trailer that he will use. He says he can fit 10 pallets into it and will then take the temperature down to about -10ºC, which should be sufficient to split the stone and produce five or six roofing squares (about 50m²) at a time. He says there might be some refining necessary to get it right.

Having carried out the necessary bat and environmental surveys and gained planning permission to re-open the mine, he has cut a new tunnel into it so he can get machinery in to extract the stone. When it was last used access and egress was through a single shaft.

The roofing so far produced looks like the Collyweston of old, which was appropriately thin. But if you want some you will have to wait. King’s College in Cambridge has already ordered 151 roofing squares of it for repairs to its buildings, which Nigel says will take all the production capacity for the next year or so. But he says there are about 2,000 tonnes of the stone under his land, which should satisfy demand for the next decade or so.