Robert Twigger is always worth reading. His gonzo Angry White Pyjamas, an account of joining a hardcore martial arts school in Japan and being put through his paces, is one of my favourite travel books. Just as fearless have been his journeys into the Canadian northwest, which he crossed by birchbark canoe, and across the Great Sand Sea of the Sahara. But he’s also a poet and can write of what he experiences with considerable finesse.

Now he has turned his attention to Britain, as many travel writers have done recently, including myself. There are good economic reasons for this. As my small local bookseller keeps telling me, people want travel books about places they can travel to. And in a shrinking world, there’s no place like home.

Twigger realises that a line heading north up the centre of the country from Dorset runs through many of its most important prehistoric sites, including Stonehenge and Avebury, right up to Lindisfarne. This provides the perfect premise for a walk, and a suitably ambitious one. He speculates that the reason