The fourth and final addition to the scriptwriting team for the third series was Trevor Hoyle, who like Tanith Lee was primarily a writer of novels - though not especially acclaimed or famous, his Q series of sci-fi books had found enough of an audience to run to a trilogy. He had also written for B7 before in a way, penning the two official novelisations based on the series - Terry Nation's Blake's Seven adapting on the opening episodes and Project Avalon, covering the initial Travis/Servalan battles. It's been a while since I've read them but despite being based on scripts rather than finished episodes my memory is they were satisfactory; Hoyle would write a third in 1981, Scorpio Attack, based on the opening salvo of the fourth series. This would be his only script for the actual show, however, and it's really not very good.
At the same time it's not exactly bad either. It just feels like a story from the Marvel comic or World Distributors annuals; it's hard to place but there's a basic lack of originality to the whole thing. The story seems like a mish-mash of plots from previous episodes and similar series with character parts to match. It's the sort of thing a fan might write after watching the show rather than the work of someone properly integrated with the production team; given the late placing in the year there's that faint suspicion that the script was commissioned as a safety net and pressed into service when something more ambitious fell through, with the expected impact on fine-tuning.
The idea of a super-brain computer organism feels like a slightly more benign version of the Altas back in "Redemption", which also gave us one of the crew disappearing mysteriously from onboard the Liberator, while a voice synthesizer was used to tempt the remaining members across in "Bounty". And naturally it's Cally who gets transfixed by Ultraworld in the first place, meaning it all but counts as another one of the times she got possessed. And also in a style which suits a man who came to the show via adapting Terry Nation scripts Tarrant finds a chap (or record thereof) who handily delivers a massive block of exposition before handily departing.
It's not just plot elements that seem dated but the characters too. Avon is all of a sudden back in his full logic mode from the first year or so, going out of his way to bang on about science and how illogical wanting to disrupt things is. While I wouldn't like Avon and Cally to be in a romantic relationship it's a bit much that in "Sarcophagus" they were explaining meaningful looks and here Avon can't even pretend to give a shit when she's kidnapped by the Ultras. Had this one happened before "Sarcophagus" or even a few episodes later it might not be as jarring and in a way it's as much Lee's fault for amping up their relationship as Hoyle's for discarding it, which means the real fault is in David Maloney and Chris Boucher running the episodes back to back without tweaking this aspect. The other way it's out of kilter with Season 3 is that no-one hostile is onboard the Liberator - which has only happened this year so far in "City at the Edge of the World", and that's only if you don't count Tarrant being a massive arsehole in that one.
Then there's Tarrant and Dayna. As the two newbies they've been paired up before so there's nothing odd there but both are written in a fairly shallow way; the sex thing is blatantly a ruse to be fair, though it hardly helps the credibility of the Ultras (three bald blokes nearly covered with blue paint and wearing boiler suits with unconvincing veins glued to them). That's par for Dayna, who at least gets some good action scenes out of it, but Tarrant is notably more heroic than he has been for the past few weeks. There's a bit of mild sparring with Avon but nothing like the pair's usual duelling. You know what I think? I think this script was written as a back-up long before and that Tarrant and Dayna's action-orientated roles (together with a more backseat role for both Avon and Cally, who spend the bulk of the episode under mental duress) were originally for Blake and Jenna, which makes the cheeky 'love' scene fit even better. Tarrant's been spiked up a bit, possibly by Boucher, but there are whole chunks of dialogue you can basically hear Gareth Thomas and Sally Knyvette reading. But it does mean the pair get to run around blowing up all sorts of shit, which is pretty cool, and Dayna gets to show off a couple of weapons.
Vila meanwhile gets to save the day and actually forms a respectable double-act with Orac. Okay, so Orac taking an interest in jokes all of a sudden only for the Liberator to randomly stumble into a gigantic brain thing in space which can be overloaded by Orac telling it jokes is bad and colossally predictable but Michael Keating and Peter Tudddenham do a good job of selling it and it's nowhere near as cringy as Vila's magic trick routine in "Sarcophagus". It is a bit of a shame that Hoyle wasn't able to write him any funny jokes, though; they're not unfunny enough to be funny either, so I'm not sure each one being rubbish is intentional, and when the plot hinges on the delivery of a series of crap puns (in a series which has a decent track record of being witty) it hardly enhances what is already a rocky endeavour.
"Ultraworld" has lots of bad bits and feels very awkward, out of step with the rest of the year, but it isn't actually outright awful, at least not relative to stupid shit like "Dawn of the Gods", and while it's hardly a polished production it's not the cheapest or worst acted either. It's just sort-of there - it doesn't follow up on anything and it doesn't set anything up, it just happens for fifty minutes and finishes. In some ways it's suffering from breaking a strong string of episodes; maybe if it had broken up that painful "Volcano"/"Dawn of the Gods" double-bill early in the year (and there's literally no reason it couldn't; in fact the crew's more cordial relationships suggest they haven't all had their fill yet) it would look better. But maybe not.