I've already had a look on the old BBC schedules site but not having any luck.
It's very half remembered. I think this was a series rather than a film. Some of this may be from a particular episode rather than general every episode stuff.
- Black & White. I think American.
- Was sort of sci-fi but not 'aliens' , more a lost world/lost civilization. Possibly repeatedly discovering lost worlds/civilizations in each episode by very unsure.
- A secret world that was accessed by rolling a massive boulder away from a cave entrance. [this could be a one episode thing rather than general]
- Some characters bare chested dressed in sort of native american indian/inca/lost tribe style - loin clothes and minimalist 'tribal' dress features like headdresses with one feather or a band round the upper arm.
- A large shiny silver metal Juggernaut (like a tank but more sci-fi modern) that was 'bad' - associated with bad guys. I remember this because it was the first time I'd heard the word juggernaut. This is how they were referred to. I remember it being as wide as the dessert passage it passed through with rocks on both sides so if it was coming, you had to get out of the way or you'd be killed.
- On BBC2 in that 5.30 - 7pm after school slot around the same time that they showed B&W Johnny Weismuller Tarzan films and Basil Rathbone Sherlock Holmes
It's possible that I've lumped more than one series in to a fake memory. I have a vague memory that it would be scary sometimes - plots with a threat of human sacrifice (but very 'clean' in that King Kong style way - a beautiful woman tided up losely by some men in tribal style dress who is wriggling around and tossing her head from side to side before the hero turns up to save her - no blood or gore it was post-school tv).
Any suggestions? I've googled a lot repeatedly over years and checked BBC2 schedule database from the 80s but they are difficult to search well.
It's definitely not:
Dr Who
The Boy from the Hidden Planet
The film The Phantom Planet