I'm just a mean green mother from outer space and I'm bad!
True story: I first heard of St. Paul's Cathedral in London because of Doctor Who. If you don't know anything about the show, you might think "that's nice." If you are a big fan of the show, you might assume that I (a young American boy in the Pacific Northwest at the time) learned about it from the classic story The Invasion with the iconic scene of the Cybermen marching down the steps of St. Paul's. But no, my first exposure to the cathedral in pop culture was from reading the novelization of The Seeds of Doom. There is a scene towards the climax where someone asks the Doctor how large the Krynoid will grow, and he replies "About the size of St. Paul's Cathedral..." Ten-year-old me had to go to the school library and look it up in the Encyclopedia Britannica (fitting!) to understand the reference, and I went on to read all about the history of the cathedral and its importance during the Second World War. So there you have it, Doctor Who achieved its stated mission of being an educational television program for young viewers!
So let's talk about the giant plant.
The Seeds of Doom - Parts 5 & 6
(TARDIS Data Core recap)
The action of the final third of the story remains almost exclusively on the property of Harrison Chase's estate while the Krynoid grows to truly monstrous proportions. There is one brief sequence in which the Doctor escapes the property long enough to go get reinforcements from UNIT (minus the Brigadier, who is unavailable in Geneva), but other than that the whole thing plays out at the single location.
There are some pretty gruesome (or at least inferred to be gruesome) deaths in the run-up to the end. A UNIT soldier gets fed through the mulching machine, and although it happens entirely offscreen you do hear his screaming right up until the end. Ultimately Chase himself comes to the same end. Being a children's program, neither sequence includes any squishing/crushing sound effects or spray of blood, but the implied violence is pretty horrific. Similarly, there is a sequence in which the the same minion who blew up the Antarctic base at the start of the story tries to escape the Krynoid and is instead dragged underwater by a blanket of animated vines and drowned horribly.
Speaking of those vines, there is another sequence in which Sarah Jane is nearly strangled to death and pulled apart by the vines being controlled by the Krynoid. This was written and filmed a full six years before the movie The Evil Dead came out, but being a horror buff it is impossible for that scene to not evoke the infamous scene from that film in which a woman is violated by living vines and branches.
So yeah, this story truly is the stuff of nightmares. By the end, the Krynoid towers over the mansion and begins to tear it to pieces before UNIT finally calls in an air strike to blow it to smithereens before it can germinate and spread its horror globally. Ironically, the Doctor plainly states that "...bullets and bombs aren't the answer to everything..." mere minutes before he ends up imploring UNIT to bomb the Krynoid out of existence. So apparently bombs are the answer to some things.
Here's a bit of trivia for you: This is the last story to feature the original TARDIS prop that had been in use (with minor modifications) since the very first episode more than thirteen years earlier. Reportedly the prop actually collapsed on top of Tom Baker and Elizabeth Sladen during filming, and finally had to be scrapped. That is a remarkable length of time for a single prop to last. By comparison, the next one only lasted four years.
This story also marks the last appearance of UNIT in any form all the way up until the Seventh Doctor. Honestly, UNIT barely even counts in this story. No Brigadier, no Benton, no Mike Yates or Harry Sullivan, just a random group of soldiers whose sole function is to fire a useless laser rifle and then call in an air strike. It is truly the end of an era in terms of setting. With only two Sarah Jane Smith stories left, the Holmes/Hinchcliffe era is now firmly established and has thrown off the shackles of the previous incarnation. This is the good stuff, right here, and I am delighted to be watching it again every day.
Companion(s): Sarah Jane Smith
Episode(s): The Seeds of Doom - Parts 5 & 6
Steps Walked: 7,265 today, 1,463,367 total
Distance Walked: 3.75 miles today, 727.19 miles total
Weight: 258.34 lbs (five day moving average), net change -48.96 lbs