I saw Assignment Earth long before I saw Dr. Who. I never really made the connection between the two until now. Further, just based on the episode, I always thought Gary 7 had traveled in time. As a kid I assumed Gary was from the 20th Century, recruited and educated by an advanced society in the future, then sent back in time to his 20th Century to carry out his assignment. As stated, the lines of dialogue always made me believe this. I mean, how else would he know that the planet he was on would be unknown to 23rd Century Starfleet? Either future time travelers came back with such information, oor else he had spent time in the future.
I assumed Gary Seven was one of the descendants of the human stock taken by the aliens six thousand years before. I also assumedówithout foundationóthat he was the seventh man named Gary in their program, and so Gary VII, actually.