In 1961 a trial batch of 24 Routemasters were produced with 72 seats, this was an increase of 8 over the original version, and was achieved by adding an extra half bay to the centre of the bus. From 1965 all remaining production switched to this higher capacity version, which was classified RML.

The RM fleet remained almost intact until the Fairs Fares ruling in the mid 1980's, which resulted in the first large scale withdrawal of the RM class. This coincided with the de-regulation of the rest of the UK bus industry, and many operators saw the crew operated Routemaster, as an effective weapon in this new era of competition.

Some surplus Routemasters were converted to open top by London Buses, these were use on the operators Original London Sightseeing tour, and later passed to the privatized London Coaches operation.

During the early 1990's the still almost complete RML class underwent a major modernization programme, while most of the remaining RM class vehicles received new cleaner engines.

In early 2003 Transport for London decided to begin the process of withdrawing all the remaining Routemasters, the last Routemasters were withdrawn from normal London routes on the 9 December 2005, however a small batch of vehicles continue to operate two special Central London Heritage routes.

The first N scale Oxford Routemaster model was released in 2008 and the model is mainly diecast metal construction.