Very on topic: Rob Grant left the show after the sixth series. I think the lack of his influence was immediately apparent, a lot of the depth was lost. Like how the transition from series 2 to series 3 got a lot more action-y, 6 to 7 started to lean more on established tropes etc (IMO).

Also of note: Grant and Naylor wrote a series of Red Dwarf novels that were surprisingly good. They really fleshed out a lot of the character behind Lister and Rimmer. One novel goes deep on the concept of Better than Life, a one episode throwaway in the show but expanded to true horror in the novel.

They split (same time as they split on the show) and wrote separate novels in different continuity in the end. IMO Grant’s was notably better.