The story so far: after a slightly bumpy first season, a second season which found a team of additional writers taking the show to new heights, and a third season which managed excellent ratings despite not featuring the title character of the show, Blake’s 7 was renewed for a fourth season, which would prove to be its final one. This was a great surprise to everyone involved, who had fully expected it to be cancelled after the third season, crafted the season finale to act as a plausible end to the story, and in the course of that finale blew up the Liberator, the starships our heroes had flown since early in season 1. Terry Nation, the show’s creator, had gone to the US to take up a scriptwriting job in Hollywood, but the BBC wanted one more season and so someone had to pick up the slack and perform a thorough revision of the show’s premise in the process.
For this season the showrunner role – to an extent that a TV show of this era could be said to had one – was arguably shared between Chris Boucher and Vere Lorrimer. Boucher, as the script editor since the start of the show, had always exerted significant oversight over the writing process, to the point where in season 1 he was effectively the unnamed co-author: Terry Nation had only intended to write a few episodes of the season but was unexpectedly tasked with the entire thing, and the only way they could make it work on schedule was for Nation to pass his first drafts to Boucher and for Boucher to whip them into shape. He’d also written the General Notes and Baffle Gab Glossary that served as the show bible for incoming writers in the production process for season 2. Nation’s exit naturally solidified Boucher’s command over the writing side of things, and this would be underlined by Boucher penning the first and last episodes of the season – slots which had traditionally been Terry Nation’s beat.
On the direction side of things, Vere Lorrimer had been a regular director for the series from the beginning, and indeed was credited as director on nearly a quarter of the series’ episodes. For this season he stepped back into a producer role, though he would step in to salvage Assassin when David Proudfoot, the episode’s director, fell ill and wasn’t able to finish it (which may explain why that episode is a bit janky).
Lorrimer was keen to shift the tone of the series, leaning into the more gritty aspects of the universe which had always been part of the show but had previously also had a significant dose of space opera camp leavening it. The destruction of the Liberator, with its fantastical technology, seemed the perfect time to update the aesthetic of the show to something a bit darker, and also perhaps made it necessary on a behind-the-scenes basis; since they’d fully expected season 3 to be the end of the show, the crew had destroyed the actual Liberator sets in the process of making Terminal, so a retcon to allow the Liberator to rebuild itself out of the smithereens it had disintegrated into wouldn’t really have helped – the interior would end up looking different anyway, so they might as well just introduce a new ship and let the Liberator‘s destruction and the death of its onboard AI Zen stand so as to not undermine the consequences of the third season finale unnecessarily.