The 9 inches to 1 mile scale of this handy atlas (at 8" x 5" it will fit in most coat pockets) provides very clear mapping for in particular the West End, the City and Docklands. It covers the central area from Shepherd's Bush in the West to London City Airport in the East, and includes the Olympic Park at Stratford. Apart from the street index there is an index of rail, underground, DLR, riverbus and overground stations, together with full details of the Congestion Charging Zone and location maps for West End theatres and cinemas. There is full coverage of local landmarks, utilities, toilets etc.
This was just the detailed atlas for Central London that I was looking for, making getting around in general, and planning of group walks in particular, straightforward and enjoyable. For residents and longer term visitors, at Amazon's price it's a steal.