The North Downs are a range of hills that run east-west from the southeast tip of England, at Dover in Kent, to Farnham in Surrey. They skirt the southern edge of London, so for a long time have offered Londoners beautiful countryside to escape to, or for a home to commute to work from. A hundred years ago, they were still quite remote, but London has grown, spreading onto Downland, and rail and road links have ensured that the many towns across the hills have also grown substantially in size. Despite development there is still a lot of unspoiled landscape, from farmland, to deep woods, to...