As national parks go, it ’s not the biggest: you can drive across it in an hour, and see the best of it in a weekend. But by car or on foot (or, ideally, both) it ’s a real adventure: savage moorland, misty mires, Stone Age barrows, and eerie granite tors (from the Celtic for tower). Enigmatic and intriguing — welcome to southern England’s last true wilderness. By Sean Thomas