But the taboo-busting kiss was far more troubling than most people remember, not because of its colour-blindness but because of its motivation. Kirk and Uhura do not kiss one another from choice. Rather, they are compelled to do so by a psycho-kinetic alien villain, Parmen, who revels in their mutual discomfort. At the same time as this kiss is being forced upon its unwilling participants, Trek fans were also coping with an unwanted smooch between Mr Spock and poor Nurse Chapel, who is writhing from the humiliation of kissing a man (and a Vulcan at that) to whom she has long been attracted. The sadism of Parmen, forcing friends into pseudo-sexual behaviour, reaches its climax in this scene: moments later, Kirk develops the necessary telekinetic power to retaliate.

But however unwanted the kiss is (and this episode, Plato’s Stepchildren, is consistently unsettling, as our heroes lose control of themselves in increasingly traumatic and degrading ways), the message for its audience is undeniable. When Kirk discusses his predicament with Alexander, a small person who is mistreated by the sadistic aliens, he explains, “Where I come from, size, shape or colour makes no difference.” In other words, by the 23rd Century, tolerance is the norm. And Star Trek creator Gene Roddenberry was determined that his audience would realise this. To quote Nichols again, “He didn’t talk about it, he just did it. It was who he was. He believed in that world, if you got it you got it. If you didn’t get it, you’d see it anyway.”