One of the most interesting things about this departure is how much angrier the Doctor is that Ian and Barbara are leaving versus how emotional he was when his own granddaughter, Susan, left (which, at the time of this dual departure in The Chase, had been the only companion departure story to compare this one to). There are several explanations for this - for one, there is (apparently) an element of danger in Ian and Barbara’s return home using the Dalek time travel machine (though one wonders how much the Doctor was exaggerating the danger given the efficiency of the Dalek machine because he really didn’t want Ian and Barbara to leave). Secondly, and perhaps more significantly, we have to remember that it is the Doctor who chooses for Susan to leave rather than Susan making the choice herself (though obviously she was conflicted) - this is actually the first instance we see of companions choosing to leave the Doctor of their own accord. Based on the evidence, the Doctor doesn’t seem to take very well to people choosing to leave him, even those people who forced themselves upon him. Look at the contrast between the Doctor calling Ian and Barbara “absolute idiots” for wanting to leave him and return home, while he sounds positively victorious when Vicki tells him that she doesn’t want to go with Ian & Barbara but to stay with him. These are some of the most “human” emotions that we see the Doctor exhibit in the series.

The use of the “time television” throughout the story is clever - it functions as a simply “wow, wouldn’t that be cool to have one of those in the future” sci-fi idea fictionally realized, it serves as a plot device to give the Doctor and Barbara warning that the Daleks are after them, and at the end it allows the Doctor and Vicki to watch Ian and Barbara’s arrival on Earth and thus know that they arrived safely. Ian and Barbara’s final scenes are perfectly charming (interesting choice to have them return to the then-present day of 1965 rather than 1963) and its fun to think that although they look to the skies and thank the Doctor, unbeknownst to them, he does actually hear and see their goodbye message somewhere out there in space.

A planned cameo for William Russell as Ian Chesterton in The Day of the Doctor didn’t happen because Russell was ill for the scheduled filming dates, but his name does feature again at Coal Hill School as the School Governor in that story, and given that Clara has quickly managed to get a job as a teacher at that school, one imagines that the Doctor talked to his own chum Ian and helped to get her the gig.

It was a fitting tribute in the 50th Anniversary story to one of original cast members, and its nice to know that arriving two years out from their initial departure in 1963 didn’t damage his career with the school in the end. We’d like to think of the same thing for Barbara. Their departure had nothing wrong with it - it was logical, emotional, bittersweet and ultimately joyful. That is why it is one of the best.