I remember being delighted to find this DVD in the bargain bins. I took it home and enjoyed the following conversation.

An Edgar Rice Burroughs adaptation starring Peter Cushing, prehistoric monsters and Caroline Munro's bikini! Sounds awesome, doesn't it? Unfortunately it's a bit of a disappointment. The monsters are always amusing and the bikinis aren't bad either, but you can't sustain an hour and a half's worth of movie just on that.

Fundamentally it's nonsense. I mean, really. That's it's job. If you're adapting Edgar Rice Burroughs and the name "Tarzan" isn't somewhere in the script, you can safely assume you're looking at silliness that a modern audience will probably assume was written in coloured crayon. In fairness to the film, it knows it's nonsense, it's proud to be so and it's not trying to be anything else. Unfortunately nothing here really matters. You can go a long way on camp value, but you could make something much goofier and funnier by editing this film down to TV episode length. The first things to cut out would be scenes of Doug McClure, All-American Hero, but keep all the shots where he's meant to be acting. Anger? Fear? Great Scott, he isn't even trying! You should also be able to get laughs from his love scenes with Caroline Munro. "I know. And I love you." You could power a small city by generating electro-kinetic energy from all the rolling eyeballs in the audience. Finally make sure you're not sleeping through the most of the scenes where McClure communicates with a caveman by pointing at his chest and saying his name, only for the caveman to reply in fluent English. Believe it or not, this isn't being played for comedy.

McClure actually made a few films like this. He was Bowen Tyler in The Land That Time Forgot (1975) and its sequel The People That Time Forgot (1977). He was also in Warlords of Atlantis (1978), which apparently wasn't an Edgar Rice Burroughs adaptation but might as well have been. The odd thing about all this is how unlikely he looks as an action hero. He's a chunky American in his forties who smokes cigars and is clearly little more than a TV actor who's done well for himself. His most famous role would seem to have been the lead in a series called The Virginian (1962-1970).

As for the other actors, there's... well, there's Caroline Munro's bikini. There's a human inside it, but let's keep our priorities here. I liked the bikinis in this film. The camera doesn't leer at them, but you wouldn't have blamed it if it had. Then of course there's Peter Cushing, but I'd been trying not to talk about him. He's playing a variation on his Dr Who from ten years earlier, except that this time he's an ex-schoolmaster rather than a family-loving old grandfather. There's definitely something querulous and teacher-like about him. This is fun as far as it goes, but it's a cartoon. I didn't believe for a second that this was a real human being.

One game for Doctor Who fans might be to pretend that this is that never-made third Amicus Dr Who film, especially given the Skaro-like jungles they find themselves in. McClure's character even calls him "Doc". The Amicus Dr Who films had less amusing special effects, of course. The problem comes with one or two politically incorrect edges to Cushing's character. Overall this film is surprisingly palatable to a modern sensibility, given how offensively they could have played the brutal slaver people. Fortunately they're not reminiscent of any real ethnic group, courtesy of snouts and Flash Gordon hairstyles. Furthermore their downtrodden human victims are multi-ethnic and the film even manages to have a black hero, even if (of course) he dies at the end. It's just a shame that Cushing's character assumes that the slavers are subhuman for no particular reason that I could see and calls them "Excitable, like all foreigners." I suppose the film's defence would be to claim that he's meant to be jingoistic and silly, as with "You cannot mesmerise me, I'm British."

What about the dinosaurs? I liked them a lot, actually. Of course they're not believable for a moment, but it's always good for a smile to see such an obvious rubber suit. They also have one or two cool details, such as the eyes that blink and the flamethrowing monster. That one was fun, even if its exploding demise was laugh-out-loud ludicrous. There's also a second cousin of Audrey 2 from Little Shop of Horrors.

No, the surprising thing about these beasties is how much blood they have. These things bleed, which I hadn't expected in a movie this silly-looking. The locals' weapons also include some nasty-looking knives and spears, resulting in fights that I certainly wouldn't call brutal but also aren't as sanitised as you'd get in a film like this today. I believe one came out in 2008 starring Brendan Fraser.

This film can be laughable, but less flamboyantly so than I'd been hoping. For example, it manages not to violate all known scientific fact thanks to some careful ambiguity about exactly how far down the mole machine has drilled. It has some ludicrously Neanderthal thought processes, mind you. When a man of Pellucidor fights another man over a woman, afterwards she will belong to the victor. Yes, even if she's a princess. If that's the case, what's to stop the biggest, randiest thug in Pellucidor turning the next generation into a nightmare of inbreeding? Or perhaps two weedy but cunning men could fight each other to a prearranged conclusion, immediately claim the spoils and then run away very fast?

The last scene with those two policemen looks like a school panto, though.