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I think Marc Platt's scripts are a bit like Marmite - you love 'em or hate 'em. I felt Susan was very badly served by the story. I did not think that her mistakes were very believable for someone who has supposedly had her experience of travelling with the Doctor, being married to a freedom fighter and being a political activist herself. I also thought that the way she and the Doctor treated Alex at the end was equally infantilising. Sure, parents and grandparents do sometimes treat their 17-year-olds like that, but the Doctor at his best is about emancipating his companions and letting them achieve their own maturity.

Finally, I'm afraid I didn't think Jake McGann was really up to it. He may well be a fine up-and-coming actor in his own right, but I wonder if (like John Barrowman) he finds it difficult to perform in the recording booth. In a couple of the crucial scenes he sounded rather like he was reading the lines in rehearsal.

Having said that, I thought that Leslie Ash and Carole Ann Ford did very well with the material, and the reunion scene between Susan and McGann's Doctor was excellent. (Even though McGann himself was unaware of the back-story.)

As for Gallifreyan / human interbreeding? I detected a couple of hints that Alex is not Susan's biological son, but adopted from a human mother. There were a couple of other lines pointing the other direction, but I thought the hints towards adoption were stronger. It was, however, unambiguous that Susan is the Doctor's grand-daughter in Gallifreyan terms (though of course one can speculate about what those terms might be). ( )