Doctor Who episode 537: Full Circle – Part Four (15/11/1980)
‘We’re all basically primeval slime with ideas above its station.’ A parable of evolution where the Deciders have been frozen in indecision for four thousand generations, repeating the same futile pre-launch procedures without ever pressing the button. Their refusal to adapt to change is finally overturned at this crisis point, as the rest of the Alzarian ecosystem rises up to cast them out. If this were made now, there would be an overt Green commentary, with the human race being expelled from the planet that birthed it, and which it has abused. I suspect there’s something of this theme lingering round the edges (it would certainly chime with executive producer Barry Letts’ instincts).