Written by Colin Baker, Interstitial Insecurity offers an interlude in between Mindwarp and Terror of the Vervoids, showing us the Doctor compile his defence case that leads into the second half of the Trial of a Time Lord. It mainly serves to fill in some of the gaps left from Trial of a Time Lord as to how the Doctor's case being presented from his future works and offers some creativity with how he selects his case within the confines of the matrix, and of course it highlights the meddling being done behind the scenes by the Valeyard to try and sabotage the Doctor's defence. It's a solid short story with no real plot, more of a deleted sequence that slots in fairly well in Trial of a Time Lord