Fusiliers In London and Throughout History - Walking and Hiking around London, London

Another good one. Walkingworld has huge library of guides with a good selection of walks, of varying lengths and grades, pretty well anywhere in the UK. The walks come in an excellent format making them very easy to follow, with photographs to illustrate every important decision point and a proper Ordnance Survey map.

A modist annual subscription gives you unlimited access to all the walks. However you can Pay As Go by downloading indiviual walks.

Crucially you can also find walks France, Spain, Norway, Portugal and Australia!