TV One of the more interesting elements of this remarkable story is how familiar, from the opening sequence onwards the Fifth Doctor and Peri are, and indeed how relaxed Peri is with the whole process of being his travelling companion.
Such is the format of Doctor Who, this isn’t an unusual occurrence. When the Doctor explains the TARDIS's dimensional transcendentalism to Leela in Robots of Death, there isn’t much continuity from the Face of Evil, the companion’s newbie status barely referred to, other than in the subtextual sense of him explaining why the ship is bigger on the inside.
Yet in The Caves of Androzani it feels different, as though this Doctor and this companion have been travelling together for far longer than a quick trip from Lanzarote.
Partly it’s the performances, the chemistry between the two which flourishes across the story. But Robert Holmes’s writing also creates a comfort and respect between the two of a kind which would ignored for much of the ensuing years when Peri had to endure the Sixth Doctor. Bicker, bicker, bicker.
Peri refers to the desert making a change from lava flows, but she also chides the Doctor for his behaviour and he admonishes her as though her rubbish sarcasm is something he’s had to endure before. But she’s not insulted. She smiles. The Doctor’s being the Doctor again.
How did contemporary audiences interpret this? Did they even notice?
Of course subsequently spin-off licensees and writers have seized on the gap between this and Planet of Fire and filled it with dozens of stories about the Fifth Doctor and Peri, Big Finish even introducing a further companion, the Egyptian princess Erimem and separating the pair for a period and giving him a completely different friend, Amy, for another search for the Key To Time.
Read or listen to any of that material and as usual our expanded universe reinforms and changes how we experience the original series as we retrospectively imagine the characters remembering all of those experiences as they’re walking around in the sand.
When the Doctor says later that he doesn’t know her all that well, but he’s willing to sacrifice himself for her, we now have to wonder if it has a double meaning.