After a disappointing first episode in the new batch of specials for the 60th anniversary expectations were pretty low, but this episode came along and an instant classic was born. Unlike other anniversary specials that cram in fan service, cameos and meta nods to the show, this episode didnt try to do anything more than just be a great new addition to the canon featuring these characters, and it's wildly successfull - it's a tense imaginative adventure worthy of anything from the golden age of New Who, with some genuinely interesting ideas and chilling moments.
