Underneath the A310 in Twickenham, in the grounds of Radnor House prep school, lies the grotto of Alexander Pope. It once looked out over the Thames, but now its view takes in the walls of the sixth-form art block and an astroturf sports pitch. But the magic of what Pope called his ‘shadowy cave’ is not lost. The grotto smells of flint. Its walls are encrusted with geological curiosities. There is a piece of basalt hacked from the Giant’s Causeway and there was once a stalagmite from Wookey Hole, supposedly shot down from the roof of the cave at Pope’s request.