I've seen the entirety of Children of Earth before, so this isn't new for me, but I absolutely love it. This first episode is easily one of the greatest openers to a series of any show I have ever seen. It does such a spectacular job of establishing the sinister threat with the kids chanting 'We are coming', and goes into some delightfully dark places, with the speech about the suicide victims who lost religious faith upon the discovery of aliens in the Whoniverse, and saw themselves as nothing but a tiny part of the universe.

I really, really like the way they up the stakes by making Gwen pregnant too. It ties in thematically with the children as the threat, and also means there's more emotional peril for Gwen. Suddenly, she's not only fighting for her own safety against the aliens, but the safety of the child she is carrying too.

Oh, and that twist with the NHS doctor who you are led to believe wants to join Torchwood, and then turns out he was a spy just trying to get in to take them down from the inside is SO great. You genuinely don't see it coming. I remember when I watched it for the first time on the way back from a Scottish holiday, it took me totally by surprise. Like the best twists, I never saw it coming.