There's not much to add from the other reviews on this drama. The only thing I would say, is that the ending was somewhat anti-climatic, it just felt like it could have ended with more of a bang, due to the build up of the finale. I don't think that I would be the only one in thinking that there was still enough room for an extra episode.
Anyhow, the drama does extremely well in highlighting the plight of Alzheimer sufferers and the effect on those around them in the wider context of it being a thriller. I think the casting was great, it was nice to see Olivia Coleman playing such a rich character in support. Obviously credit goes to John Simm for providing an outstanding performance of great depth, as well as Jim Broadbent's lovable portrayal as the father suffering from Alzheimers. Also, Kate Magowan oozed an unconventional sense of sexiness from her first scene behind the bar.
I am glad to have watched this show and I shall be recommending this to all my friends!