"efficiency" will result in greater pollution, brainless brainwashed humans, and more death and disease. The Doctor then uses his blue crystal to break Stevens' hypnotic state, and Stevens, infuriated at what the BOSS has done to him, cross-feeds the generator circuits, causing the whole plant to explode, killing Stevens and destroying the insane computer. The menace defeated, UNIT troops and environmentalists gather at the Nuthutch for a celebration made all the more special when Jo and Jones announce they are getting married. The Doctor gives his blessing and gives Jo the blue crystal as a wedding present, but since this means the end of Jo's travels with the Doctor, he is evidently upset by the situation and quietly slips away while the party is in full swing. As Jo and Jones dance, the Doctor drives Bessie off into the sunset. Production In the footage of the maggots around the quarry site, several of the maggot props were in fact inflated condoms (some inflated with air, others with water). The colliery used for filming was Ogilvie Colliery near Deri, Caerphilly, while Global Chemicals was the RCA International factory in Brynmawr. The script required the Doctor to state that the maggots have "thick chitinous skin". Pertwee asked producer Barry Letts how to pronounce the word, and Letts, unaware of the term, told him to pronounce the first syllable "chit", rather than the more correct "kite". Two days after Episode 4 was broadcast, Letts received a letter consisting simply of the words, "The reason I'm writin'/Is how to say kitin ." The prime minister is addressed as "Jeremy", which was a production joke referring to the then Liberal Party leader Jeremy Thorpe. In 2004, Barry Letts said he was unhappy with the colour separation overlay effect used for the cavern scenes in this story. Cast notes Tony Adams, who played Elgin, was taken ill during the recording of The Green Death, and so Roy Skelton was brought in to play a new character called Mr James, who was given the lines written for Elgin. In Global Conspiracy (see 'Home media'), Adams actually uses his real illness as an explanation for his character's sudden absence towards the end of the story. The part of Professor Clifford Jones was played by Stewart Bevan. Bevan was at the time engaged to Katy Manning. The fictional couple become engaged at the end of the story, whereas Bevan