The 1970s were a strange time and both Doctor Who stories featured on the latest DVD release capture something of that peculiarly paranoid decade. As Matthew Sweet suggests in the documentary accompanying Invasion of the Dinosaurs, even the writers working on Doctor Who during that decade weren't immune to chucking social commentary into the mix to provide a counterpoint to Pertwee's flamboyant action man about town and Baker's time traveling bohemian.

With Barry Letts and Robert Sloman making room for transcendental environmentalism or Brian Hayles cheekily raising an eyebrow at the European Union and the miners' strike, the series was at its most 'political' in the early to mid 1970s. This is despite the fact that it's taken a few decades for Terrance Dicks to grudgingly acknowledge that "anything a writer thinks or feels is bound to come out in his work" and that such a subtext existed within the series he was script-editing. Perhaps he wasn't as left leaning as his old mentor and friend Malcolm Hulke who, out of all the writers working on the show, made such a virtue out of wearing the colours of his social conscience on his sleeve.