I am well aware that the concluding story in the Key to Time arc is not highly regarded in Doctor Who fandom. But I unashamedly include The Armageddon Factor in my top 100 (albeit it at the bottom end) as a story I manage to get great enjoyment from. I grant you that as with The Ribos Operation and The Power of Kroll, it would probably be less enjoyable were it not for the overall story arc for Season 16. But the fact is, it is the concluding episode of the season long story-arc, and a very satisfying conclusion at that.
In reality, there are three different stories at play here – two warring planets; the Doctor trying to find the last segment of the Key to Time; and an agent of the Black Guardian, the mysterious Shadow attempting to steal it. There are some nice twists at play too – the planet Atrios is on its last legs under the command of a mad military office the Marshal, whereas the planet Zeos is effectively run by a battle-computer. The Shadow lives on a planet hidden between the two planets, manipulating both sides (although it isn’t actually clear why he needs to do this) and plans to use the Doctor to track down the last segment of the Key to Time – which turns out to be none other than Astra, Princess of Atrios!
Okay, so at six parts it is rather long. The love story between Astra and Merak is rather poorly done, and the Shadow’s methods seem haphazard at best – but you still find yourself enjoying it! There is something rather awesome about the Doctor manufacturing an ersatz sixth segment in order to stop Atrios and Zeos blowing each other up (if ever there was a metaphor for the Cold War …), and the final scene where the Doctor faces off against a disguised Black Guardian is genuinely spine tingling. We also get a brief glimpse into the chemistry to follow in coming seasons, with Lalla Ward appearing as Astra. Just one story later she would replace Mary Tamm as the newly regenerated Romana – although it again is a regret that we never get to see Romana regenerate properly.
As the end to Season 16, The Armageddon Factor is entirely worthy and I greatly enjoy it. As a standalone story however, it is rather obvious why it’s not in the top 50 …