"Take us home Doctor."
And the Doctor would attempt to comply. He would push the buttons, turn the dials and cranks, push the levers, and put in the coordinates that they were to go back to London. He would say that he could not wait to, that they had been nothing but trouble since he had met them. He would be completely confident of the fact, because – after all – there was nothing that he could not do on this ship. And she would do as he asked and they were likely to be back there in no time.
And the Doctor was actually upset. He would pretend that they were a nuisance that he could not wait to get off of his back. He could pretend that he was an old man that could not deal with such bothersome people as the two school teachers. But in reality, he would be very stricken with sadness. He would never admit becoming fond of two Humans, but somehow it had happened. And he dreaded the day that they returned to London, because then he would have to accept their leaving him.
And the Doctor would open the door to see another planet, another time, another everything. They would complain and tease about his control over the Tardis. They would finally give in when he wanted to explore the newest place, as he had yet to come to a place with no radiation and an atmosphere without examining it himself. They would finally find themselves head deep in whatever was going on, as he had, and nearly have as much fun as he did in trying to discover out the answers. And in reality, be glad for the bit more time that he was granted with these people that he never thought he would become friends with.
And then they were gone. Found their own way home. Were as upset as he was about their leaving, but unlike him would not be left without them. They had someplace to return to, that they had to go back to. If anything, because it had been their plan all along. He would be left behind. And it was a strange feeling for someone to be leaving him, instead of him leaving them, for even he had left Susan behind on Earth.
And the Tardis would mourn. Because despite the fact of how he ignored her when those people were aboard, she had done her best to keep them. For her Doctor's sake.