A unique episode of Doctor Who which served as a Doctor-less prologue to the 12 part The Daleks’ Master Plan which aired some five weeks later. Though the story has long been lost from the BBC archives, a few stills remain which afford us a glimpse of the representatives of the 7 planets which are in cahoots with the Daleks.
And among them, if we look closely, we can see that one of the unnamed aliens is wearing a space helmet that looks a lot like the kind worn in the Pathfinder to Mars series and which, as you will have already read, goes on to feature fairly regularly throughout the whole of the 70’s Doctor Who. I wasn’t sure at first if the plastic visor was in place although the position of the air-hose does seem to suggest that it might be. In Pathfinders it was replaced with a cross of wire so as not to muffle the actors voice although I don’t think this alien has any specific lines so that isn’t really an issue here.
I think this is most probably the first outing of the prop on Doctor Who, although having only spotted it’s use a couple of days ago, I’m not going to put any money on that.