The RT-type
The AEC Regent III RT (RT-type) was first built in 1939 and was designed for & by London Transport. It was the standard red London bus during the 1950s, with a total of 4,825 buses built for London Transport. Although not all were in service at the same time.
Some RT-type buses were built for operation outside London, such as St. Helens Transport.
Read more about this topic: AEC Regent III