The walks in this guide are all within the circumference of the M25 motorway. Many people, including Londoners themselves, may be surprised by how much open, attractive and unspoilt countryside still survives in an area that is often thought to comprise little more than sprawling suburbs and congested roads. The walks fall into three main categories: urban, suburban and rural. Many of these have an unexpected solitude and tranquillity normally only experienced in remote and thinly populated parts of Britain.