Many of the review with and without spoilers talk in great detail about this episode and I'd recommend reading them. I just wanted to write about the brilliant acting job of Jacqueline King as Donna's mother. Throughout the series she's been a sarcastic biting presence. With this episode we see that her personality was a brittle shell protecting a scared vulnerable person and her breakdown is subtlety and beautifully portrayed by Jacqueline King. Kudos to this fine actor.
