It's widely recognised as the best era of the Classic Series (maybe even of the entire series) but if any era of the old show steered close to being too dark for a family audience, then it's the Hinchcliffe and Holmes period. Just compare The Ark in Space to Robot to see the very different approaches of Philip Hinchcliffe and Robert Holmes and former team Barry Letts and Terrance Dicks, or the teams' differing versions of the Master. Utilising concepts and motifs from classic cinema horror, the pair traumatised children for three years and upped the violence with Zygons being impaled on pitchforks and companions being mauled by giant rats. No, seriously. This era led to the famous campaign of self-proclaimed moral watchdog Mary Whitehouse. In particular she was scathing of the team's decision to freeze frame the Doctor being held underwater by Chancellor Goth at the end of episode 3 of The Deadly Assassin. This led to the producer getting a dressing down by the top floor and to Graham Williams being instructed to tone down the horror when he took over.