The 5 was the route number when the route started and the destination was indicated as Perry Common. The bus terminated at the Ring (Enderby Road). Once the Witton Lodge council estate was completed, the buses were extended to Court Lane as the 5a, but the 5 was still the more frequent route for a time, until eventually at the beginning of 1939 I think (Radiorails will I think be able to date it exactly) ran regularly as the 5a as the Perry Common Court Lane and the Perry Common 5 was a peak period bus. Eventually (?date Radiorails?), the 5a became the 5. After 1962 I dont know what happened.
Bob