Another christmas special already? Blimey. This was a sweet little episode that gave Alex some much needed characterisation and built upon the Doctor and Susan's relationship in a meaningful way - as well as how she's grown beyond him. It was interesting seeing the Doctor treating Alex as a sort of surrogate Susan and trying to get him to come in the TARDIS with him the entire time, and it was paid off well with him deciding to go travelling and make his own destiny with Lucie. Poor 8, alone again. 7.5/10.