I don't think much knowledge is needed when driving a cab .. be it London or the suburbs..
Most use a Sat-nav.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Srumpy, Even black cab drivers might use a sat nav at times, but the fact remains, in order to get their Hackney cab Licence, they will have had to sit with an examiner for some length, and accurately describe most London routes. and their locations.