"This story was carried by the main characters" is an odd thing to say, given how stories work, but there is a reason I enjoyed Frontier in Space and it wasn't the plot (anti-war storyline started strong and weakened with each episode), the side characters (forgettable), or the aliens (very racialised in design, most obvious with the Ogrons, who are a few small steps removed from blackface, but also with the Orientalism in the Draconians)

It's a shame this was Delgado's last story. Obviously, they couldn't have known he was going to die, and fair play the interactions between the Master, the Doctor, and Jo really make this serial, but it's a but of a flop to end in