A strong story, let down by a couple of things. Firstly: I Don't Care About Owen Harper. I see what they're doing with his character, I can even respect it, but ever since his first appearance he has not been written in a way that has ever appealed to me. (This is a purely personal issue, I acknowledge)

The second is a perfect example of the truism "aged practical effects look charming, aged CGI looks Bad." The CGI looks bad, to the extent it undercuts all tension. I'm a Doctor Who fan, I'm used to bad effects, but this was pretty low