Chris Bidmead (who wrote Tom Baker's swan-song Logopolis) as script-editor, & John Nathan-Turner, as producer of Doctor Who, favoured a return to 'hard' sci-fi (that is, the foregrounding in the narrative of quite elaborate & difficult scientific concepts such as Charged Vacuum Emboitments) for Tom Baker's final season. Hence this 'trilogy' - very loosely framed by the Doctor & Romana becoming trapped in E-Space, a smaller universe somehow external to our own, & having to escape from it back into our N-(normal)-Space. I'm ambivalent about the merits of this approach. The final story in the trilogy, Warriors' Gate, has, to my mind, a near-incomprehensible denoument, and throughout lacks proper attention to the basic story-telling. Script-editor, writer and director all laugh on the commentary-track about how now it's on dvd you can watch it over & over & perhaps finally understand it, but the fact is that it barely makes sense, & less chat about CVEs and the like, and more attentio to dramatic & psychological density and depth, would have produced a more gripping result.
Interesting, in State of Decay, the vampire story, Bidmead rewrote Terrance Dicks' script massively (to Dicks' chagrin) in line with his more science-fictional vision and the director, who'd originally agreed to direct the story because of its Hammer-Horror gothicism, refused to do the job unless they went back to Dicks' original script, which they did - a singularly rare occurrence in television or film. Dicks does concede that Bidmead contributed the entertaining rocket denoument.
Everyone is quite candid about Tom Baker & Lalla Ward's tempestuous off-screen relationship, pointing out that on a bad day Tom refuses to look at Lalla in their scenes together. Lalla is fairly cold about Adric as a character, & I did feel a bit sorry for Matthew Waterhouse being thrown into such an emotionally-wrought setting. He himself in his interviews is quite endearing and unpretentious.
Rewatching the stories I actually enjoyed all of them: all contain nice ideas and the odd sharp line and image, and Lalla's outfits are rightly celebrated. But I found the pace and use of language stodgy by comparison with the Graham Williams/Douglas Adams stories. I was also struck by the similarity of set-ups in all three stories. In Full Circle the characters moulder away in an endless round of pointless maintenance chores on a crashed Star-liner. In State of Decay the vampiritic Lords moulder away in courtly parasitism in the ruins of a crashed rocket. In Warriors' Gate the crew moulder away on a crashed space-ship unable to escape the inertia of their situation. Perhaps this reflects that late-70s sensibility that Britain itself was mouldering away inertly, the crashed ruin of its imperial glory...
I like actors, so didn't want to find Adric such an unappealing character on re-viewing his debut, but I just don't take to Matthew Waterhouse's performance. But then I also feel he wasn't really given a proper character to play. Nathan-Turner's original concept was of an 'Artful Dodger' - but then he cast the utterly public-schoolish Waterhouse - who wondered after being offered the part if he was going to be asked to affect a Cockney accent. Certainly there seems to have been little attempt to integrate him psychologically into the trilogy - Tom & Lalla don't become stand-in parents or older siblings or scary magical figures to Adric: everyone just blodges through the dialogue, which is somewhat randomly assigned.
Everyone seems to hate poor old K-9, who is rather side-lined here.
Overall, I enjoyed the E-Space Trilogy but feel that the price of pushing up the level of scientific conceptualisation proved to be letting the psychological maturity of character & dramatic situation deteriorate.
Interestingly, despite a certain amount of technobabble, the next story, The Keeper of Traken, worked almost entirely as a fable and has almost no scientific feel to it at all: it's only with Tom Baker's final story that Bidmead gets to fully express his vision for the show - & does so very effectively, I think.