Poor Old Mike Yates
After three years of apparent infatuation with Jo, she's grabbed out of his clutches at the last minute by some flash scientist with long hair who grows fungii. Typical. 'The Girls' is probably one of the reasons Mike gave on his application for joining the army. Then when he channels all of his efforts into Jo, the one girl of his dreams, she goes into the jungle with some hippie. And he's inadvertently wearing a suit just to symbolically demonstrate how 'straight' he is. Again, typical.
These are the forgotten moments of a scene whose emotional effects are usually attributed to The Doctor. For a series that often had a reputation for running rough shod over human feelings, here are Letts and Dicks giving time to something which has simply been an undercurrent in a few previous stories, and making Yates something of a tragic hero (presumably to aid the justification of his rail falling later).
This is just one of the many moments which can be quite happily thrown, flan like, in the face of anyone who perpetuates the myth that classic Doctor Who lacked sentiment. Some of the praise that greeted the new series included pleasure that for the first time ever it plucked the heart strings, with the Dalek's demise in Dalek being cited as an example. It's something that is relatively evident in every story in both new seasons, as people die usually in fairly horrific ways.
The difference in the 'old' series is that the best of such moments are unexpected. Yes, there were the events, Sarah-Jane leaves, Tom regenerates, Adric smacking into a planet, in which tears were positively encouraged but arguably just as effective, if not more so, were the quiet times, mid-story when a companion, would all to rarely give lip surface to actually how they were feeling long term about something.
For a split second, and Yates gapes and drops his head then looks up grinning, and there is genuine sorrow for him, at a time when the audience should really be sad to see the back of a popular companion.
In The Tomb of the Cybermen for example, although the image of the defrosting hoard arguably sticks in most memories, there is also a lovely scene in which Victoria reflects on the loss of her father in previous story; it has little to do with much of anything else happening in the story but it feels real and human, and as a side note Troughton, often remembered as being a but of a shouty clown, was for once able to present some understand and subtly, something that the programme at the time predominantly failed to tap into.
This a similar pattern to The Green Death, as nowhere has Mike's love for Jo been signalled -- indeed this is one of the rare occasions when they're even in the same room together. The point is that for the purposes of the drama, Mike needn't be wearing his heart on his sleeve. The rest of the story, amid the mad computer and viruses and giant maggots has been about Jo falling for Cliff and vice-versa. Mike simply hasn't been in the frame.
For a split second, and Yates gapes and drops his head then looks up grinning, and there is genuine sorrow for him, at a time when the audience should really be sad to see the back of a popular companion. It continues through the rest of the ensuing scene until the Brigadier's pat on the back, which is a pleasure. Watch Franklin - Yates has been given a heart blow and he's showing it, each new bit of exposition from the research grant onwards wounding him.
That the Brigadier is the one to console him, revealing that behind the gruff, the cap and the moustache is a man who is actually paying attention to the lives and feelings of his officers also gives Lethbridge-Stewart a dimension that wouldn't be apparent again until Mawdryn Undead some years later. What's usually forgotten too is that this is Mike's final few moments as part of the Unit family - he's a traitor in Invasion of the Dinosaurs and in seclusion in Planet of the Spiders - so this would also be the last moment we witness them in a moment of mutual respect. From then on, everything would change.