TTT4 - The Green Death 4

This story really is the original UNIT's last hurrah in Doctor Who. Sgt. Benton takes charge of the demolition at the mine (his duties have increased since his debut - possibly the only UNIT regular who could make that claim). The Brigadier does his best with not as much success as he'd like to see, but instead of general stupidity, it's the Prime Minister himself who thwarts any headway that he's trying to make at Global Chemicals.

But just when we think the Brig is down and out, he pulls a rabbit out of a hat - surprising everyone by managing to sneak Captain Yates into the upper floors at Global Chemicals, disguised as someone in the government. As such, it's great to see Mike in an expanded and unique role after taking the first half of this story off, especially given that Yates wasn't even in the other UNIT story this season, The Three Doctors. His covert conversation with The Doctor and the Brigadier (especially when he calls his superior "Lethbridge-Stewart, my dear fellow") is one of the best things about this episode.

Another great thing? Jon Pertwee's quick return to comedy, first disguising himself as a Welsh milkman, then as the cleaning lady, Doris, in order to try and infiltrate Global Chemicals himself. Everybody seems to be letting their hair down this story (and, judging by the haircuts of some of the soldiers and officers, UNIT has obviously got a head start in that category), and the result is magnificent.

Just when you think this story can't get any better, we finally meet the BOSS - a sentient computer running Global Chemicals while humming Wagner operas and forming a great double-act with Stevens, his "little Superman". Their banter has been great throughout this story, but now that The Doctor has stumbled upon BOSS's lair, the resulting conversation is keenly anticipated.