The grey afternoon light falls on the surreal moonscape of mid-Cornwall's industrial clay country. Nearby are the artificial paradises of the celebrated Eden project, golden sandy beaches, and picturesque fishing coves. But these barren, unprepossessing looking highlands hide something far more interesting: if there were such a thing as a 'geological ghost', Roche Rock would be it.

Perhaps it's the way it sits there, seemingly blending in with the colour of the landscape, until you realise that it's too big, it's too imposing and that discovering it is too sudden; reaching the island-like crag of Roche Rock takes the visitor by surprise.

To find this unusual outcrop, take a left turn off the A30, eight miles (13km) south-west of Bodmin, towards Roche (pronounced 'Roach') village.