On the surface after 1945 > Turning London's transport around
Before the war it had made sense to convert trams to trolleybuses because the same electrical distribution system could be used. By the 1950s the power system itself needed replacing. It seemed cheaper and simpler to use diesel buses instead.
London Transport designed a new diesel bus and unveiled the prototype in 1954. It was named the Routemaster. Production models entered service from 1959, replacing the entire trolleybus fleet by 1962.