Toxin-tolerant plants take root in colliery's spoil tips

Middlehope Moor, Weardale Miners who left waste rock beside the burn created a perfect habitat for the spring sandwort

On a grey day in a tree-less landscape, buffeted by a bone-chilling north-easterly wind, only the calls of curlews and oystercatchers that had returned here to breed suggested this must be spring.

But when we reached the stony, undulating, ground near the entrance to the "governor and company's level", a mine tunnel driven into a hillside almost two centuries ago by the London Lead Company, we found an infallible floral indicator of the season.