The STL Type bus was introduced in 1932, and was considered the first really modern London double decker bus, and was so popular nearly 2650 were built, mainly put to use in London, where their popularity in being able to adjust to the rapidly expanding routes required for the ever increasing population meant they were favoured by London Transport over more old fashioned trams that were fixed in their travelling routes.
AEC STL Bus
The original STL models had 60 seats but was quickly reduced to 56, and was the standard double decker seen in London for over a decade.
AEC STL Bus - Side View