Following on from London Bus Routes One By One: 1-100 and London Bus Routes One By One: 101-200, this third volume in the series explores what used to be the old London Transport's highest-numbered block of routes. These numbers were once reserved for single-deck services, but the weight of post-war expansion soon filled in the sequence. As in previous volumes, a potted history of each route is accompanied by a list of points served and one or two pictures of the kind of bus that can be found in service today. The pace of tendering and Transport for London's imperative towards emissions-free propulsion has meant increasingly rapid turnover of bus models, which are expected to last the length of two full-term contracts of seven years before replacement. Illustrated with over 190 color photographs, this volume represents an up-to-date snapshot of the fascinating modern London bus scene as it stands in autumn 2021.