Dr Who tackles climate change, corporate power and the world food crisis

The Green Death screened in 1973 was a slice of effective Green Party politics, very enjoyable (other than the dodgy hair cuts).

Evil corporation, illegal waste dumping, insane computer (who quotes Nietzsche and hums to Wagner), hippie heros and giant killer maggots.

In short perfect viewing.

The BFI notes:

Unusually, the hazard in The Green Death comes not from extraterrestrials, but from the greed and callousness of a large company, Global Chemicals. Its manager is unmoved by the deaths of miners caused by crude oil waste from his plant. He even obstructs an investigation, fearing the plant will be closed down. By ruthlessly pursuing profit at the expense of human lives and the local environment, he represents the audience's worst fears about scientific progress and 'big business'.
The early 1970s saw a gradual undermining of public faith in the industrial and technological programmes of the 1960s, alongside mounting social unrest. The protesting miners depicted in The Green Death foreshadow their real-life counterparts in the 1974 miners' strike. Most of the chemical plant staff, however, are brainwashed into obeying orders without question, and when one resists, he is forced by the plant computer to kill himself. These mindless, dehumanised workers refuse to take responsibility for the deaths and environmental damage their company is causing: they are simply 'obeying orders'.
By contrast, the free-thinking Nobel-prize winner Professor Clifford Jones (Stewart Bevan) is an advocate of moral and ecological responsibility in science, warning of the dangers of industrial waste and cultivating rare mushrooms in an attempt to solve the world's food shortage.