There was always the Open University. Worthy films about the development of Britain's transport infrastructure in the 19th Century. BBC4 with lower production values.
Open University chemistry programmes were my absolute favourite telly when I was about 5. Not only did you have tweedy scientists doing exciting things with balloons
[1], but they had the magic blackboard where important-looking equations appeared to explain what was going on. I can't imagine I had a clue about the
SCIENCE, but I found the idea that if I watched enough of them I'd eventually understand *everything* immensely compelling.
The complete opposite of Chris Tarrant.
[1] I was used to phenol-scented scientists doing boring things with petri dishes.