Re Michael Caine.His first role according to IMDB was in a film made for the BBC called "Morning Departure" which was shown on television on 1 December 1946. It was remade as a film a few years later though he wasn't in the film, IMDB describes his character as "Teaboy".
IMDB's cast list for that 1946 BBC version has quite a few well known actors in it:
https://www.imdb.com/title/tt0...s?ref_=tt_cl_sm#cast
Note that the Radio Times listing for it (via the Genome site) omits all of the well known actors other than Nigel Patrick, Patrick Macnee and Michael Hordern, so no mention of Michael Caine, Richard Attenborough, George Cole, John Mills or Kenneth More. Richard Attenborough, George Cole, John Mills and Kenneth More were in the 1950 film version. So there has to be a question mark of IMDB's accuracy. However it is reasonable to believe that Michael Caine was in the 1946 BBC version. One of my film biographical books mentions that he was in a lot of TV programmes during the 1940s before going into films - he would have been 13 at the time so a teaboy would be the sort of role he played then.