In this case, he said the girl looked 15 or possibly 16. In the days before Labour introduced the 'position of trust' law that made sex with under-18s illegal for such adults, it would have been a brave call by the producer. She could easily have been 16 -- perhaps she actually was -- in which case Savile would have been in the clear and the producer would have been looking for new employment.
This was what I was thinking too – I think a lot of people are thinking about the current (or even American) legal situation and forgetting it isn't necessarily that simple. It was different then - and not all legal systems considers sex with a minor rape
per se, and what is a minor also differs from one legal system to another (historically and geographically). That is not to excuse anyone who didn't speak up (and certainly not JS himself; I'm almost ready to start believing in hell just for him), just to remind us that maybe some people actually
did speak up, but it didn't do any good.
Attitudes have changed a lot in the past decades. When I went to school, there were teachers well-known for inappropriately touching girls (prepubescent girls even) and the attitude was just "well, stay out of his way." Today that wouldn't be tolerated for a second.