We try to find safe well-established car parks. Where there is no car park available, sometimes roadside parking is necessary. Most car parks are large and safe but occasionally we use a small isolated car park. If you park in a small isolated car park, take precautions against thieves: • leave nothing on the seats; • indicate that your glove compartment is empty. The West Sussex police issue a large windscreen card which says At the advice of the police, nothing has been left in this car.
When doing a monster walk (15-30 miles) one excellent trick is to start at opposite ends, meet up in the middle and swap car keys.
A good number of walks can be reached by train. Look for the ⇌ sign beside the title.
Most country walks are on a bus route but unfortunately it is very rare to find one that runs on Sundays. Always check the timetables: every route has a timetable on the web. One big advantage of buses is that you can shorten a circular walk. No problem in London of course.