In Edwardian Britain the stage is set for a grand new drive to tunnel through this Welsh mountain with the aid of a drilling machine which doubles as a vehicle. It is the hope of its inventors, industrialist David Innes (Doug McClure) and professor Abner Perry (Peter Cushing), that they will be able to take their next excursion into the bowels of the planet itself, though that plays out sooner than they expected as once they begin to drill, they go off course and head down, down, deeper and down. Passing out with the heat, they wake up some time later to find themselves many miles beneath the Earth's crust...
So it ended here. At the Earth's Core marked the final entry into British production company Amicus's canon, occurring just as their great rivals, who they never really bested if truth were told, Hammer were winding down as well. It didn't end very well for Amicus, with tales of acrimony and misappropriation of funds, but the creative powerhouse behind them, writer (or adapter more usually) Milton Subotsky did continue to operate in the industry for a while afterwards. This was one of those co-productions they had set up with America's AIP, all destined for the drive-ins of that nation, but has gone on to a reputation as one of the most enjoyable, non-horror portmanteau efforts they ever made.
Not because it was any good, but rather the opposite: it was so bad it was good. Much of that regard was down to the special effects, which were downmarket but had a budget verve and ambition which rendered them endearing, yes, those subterranean creatures were basically men shuffling around in rubber monster suits, but you had to admire Amicus' enthusiasm in bringing them to the screen, much as they had done with The Land That Time Forgot, also starring McClure in one of a loose series of four fantasy adventures he made around this era, and all with a British connection which has made him something of a minor hero to those who appreciated his efforts.
Cushing was evidently glad to let his hair down, what was left of it, in a more comic role as the scientist who can tell you what kind of flora or fauna you're looking at, but the truth of it was that in adapting one of Edgar Rice Burroughs' Pellucidar novels they ended up with something more akin to a big screen Doctor Who story - by surely no coincidence Cushing had starred in two of this company's feature versions of that famed television character. Not only that, but the production design of the undergound jungle resembled quite closely that of the Who tale Planet of Evil, though that was no bad thing, as part of the enjoyment rested on the imaginative design, at points more so than the actual plotline it was delivering.
Also worth a look, or worth a listen, were Mike Vickers' music and audio effects, where they really went to town: weird bleeps and bloops, the evil tribe's guttural babble, and that "backwards cymbal" sound whenever we saw the actual villains, those psychic, carnivorous reptile birds the Mahars, a sound the film is so in love with that it repeats it at every opportunity, along with a closeup of a glowing eye blinking to underline the supernatural thing going on. For those less impressed with such paraphernalia, there was always Caroline Munro as the Princess Dia to appreciate, in regulation skimpy outfit complete with (prehistoric?) eyeliner, though she disappeared from the film in the middle section. Handily, everyone spoke English too, which would have been a good opportunity to ask the good tribe why so many of them sported very drastic perms - one even has a green perm for reasons best known to himself. So it was all very silly, but you could see why so many indulged in its cheerful cheese.