Whooverville 2 - Serendipity

Luke Harrison [The Minute Doctor Who Podcaster] has unearthed an ancient artefact, the BBC Book Serendipity, with a forward by Katy Manning.
Katy had presented an arts and crafts show of the same name following her last appearance on Dr Who in The Green Death in 1973. She was asked about this during her interview at Whooverville 2 and her response can be seen here thanks to Tim Drury.

The title of the show also came from The Green Death. Oddly enough a friend of mine recounted her earliest memory of Dr Who, a blue snake the night before whooverville! I racked my brains and eventually concluded that the only blue snake in the show, that fitted the time line was featured in The Green Death. The Doctors first visit to Metebelis 3. Here is the video..

Here is the plotline that explains the happy accident.. .Jo has alienated Jones, with whom she is falling in love, by ruining one of his experimenting slides of green slime. Determined to make amends, she heads to the slagheap in search of a maggot to run some tests on. Meanwhile, Jones finds that the fungus powder Jo spilt on the slides is actually a cure for the 'green death' infection. He races to the slag heap to find Jo surrounded by giant maggots, and they are both caught in an RAF bombing raid on the maggots. Jones is infected with the 'green death' and begins to turn green — and all before he was able to share his knowledge of the cure. Jo contacts her UNIT friends with her radio, and the Doctor and Sergeant Benton rescue the two from the maggots in Bessie. Hearing Jones utter the word "Serendipity", the Doctor realises that Jones might have stumbled upon something that could combat the maggots and their infection. Benton arrives with a maggot crysallis - proof that the maggots are beginning to transform into mature giant insects. Then, the maggot that escaped from the laboratory is found on the table - dead. Realising that the creature died from eating some of the fungus, the Doctor also discovers the cure for Jones.