With all the children of the world, or at least the most vulnerable among them, at stake, what will Torchwood do with no base and no influence?

This was a complete game changer for Torchwood. For the first time, in large part due to the increased focus from Russell T Davies, it was able to briefly outshine its parent show over 5 evenings with some of the best drama ever seen in the Doctor Who universe. All improvements between series 1 and 2 of Torchwood feel like a drop in the ocean compared to what was achieved here.

There are moments that in retrospect feel clumsier than they did in 2009 but no-one could deny the sheer power, raw emotion and dramatic brilliance of the final episode and a half of Children of Earth. Ianto’s tragic arc is rewarding - in part thanks to the excellent introduction of his wider family, bedding in his character before seeing him off. Jack’s daughter and grandson provide an even more chilling arc ending with the terrible but compellingly reasonable sacrifice that Jack Harkness must make. But most strikingly of all, Peter Capaldi’s civil servant character and his family provide the most awful and memorable blow in the show. These are all story beats which would be far, far too much for Doctor Who.

I know certain types of Doctor Who fans over-emphasise the positive qualities of the darker sides of the show, but this is a definite case where shocking themes are married up with brilliant writing. RTD has a knack for writing tragedy and the 456 as an non-relatable but believable menace, provides the perfect set up and payoff.