(1952, Anna Neagle, Michael Wilding et al)

Drama about different folk travelling to the Epsom Derby by different means of transport, which is intercut with documentary-style footage of the event itself,presumably from 1951.
Lots of blurred vehicles moving too quickly to be identified for sure, but this is London Transport Green Line RF93 (LYF444):

Buses in traffic are also too distant to identify:

Burlingham bodied, but no front badge on this fully fronted coach:

London Transport: a late model AEC STL, a Leyland RTW, RTW329 (KXW429), and a trio of Leylands:

Leyland Tiger:

A fully fronted AEC, probably a Regal III:

Anonymous interior with back projection:

I believe this is Homeland Tours HRK906, a Leyland Comet CPO2 with Strachan coachwork:

One of a large batch of AEC Regal O662s with Windover body new to Timpson of London in 1947:

Blurred London Transport AEC STL:

Leyland Royal Tiger:

Commer Commando:

Views of the parked coaches around the course:

….and the starter climbs the steps to set the Derby running: