Shared universes are such a big deal currently. With Marvel, DC, LEGO and Sony all offering them as of recent, it's easy to forget that Doctor Who did it first with Doctor Who, The Sarah Jane Adventures and Torchwood. Like Marvel, it was successful.

The Stolen Earth/Journey's End is a typical RTD bombastic finale and it's all the better for it. The plot sees RTD Era companions and allies of the Doctor attempting to contact the Doctor via the Archangel Network to ask for his help with the Daleks' latest invasion of Earth. Davros and the Daleks are planning on unleashing a reality bomb on all universes (including Pete's World seen in Rise of the Cybermen/The Age of Steel and briefly in Army of Ghosts/Doomsday) in an attempt to destroy reality with the use of twenty six planets and a moon to transmit it (one of them being Earth). There is no doubt this story is completely barking mad but this makes it all the more enjoyable. The two parter feels like a comic book; maybe not a DC one but you could easily imagine Marvel doing this as an Avengers story (well, with Red Skull and Hydra agents instead of Davros and the Daleks).

The inclusion of the spinoffs is also handled nicely; none of them feel shoehorned in and every character seems like they should be there. What's even more impressive is how Russell T Davies managed to include Torchwood (a show that the BBFC rated 15) in such a respectable and family friendly manner. The Torchwood characters don't even feel restrained by the primetime Saturday night slot. Many of the spinoff characters are reduced to small parts (none of them actually join the Doctor but help from the sidelines, so to speak) but it's just great to see them in the main show. Mr Smith, Luke, Gwen, Ianto... who didn't want to see any of these characters appear in Doctor Who back in 2008? It's the same thrill that many get from seeing Iron Man, Captain America, Hawkeye, Black Widow, Thor, Hulk and now Spider-Man onscreen together.

This story features one of my favourite scenes: that of the Doctor, Metacrisis Doctor, Sarah Jane Smith, Rose Tyler, Jackie Tyler, Mickey Smith, Martha Jones, Captain Jack Harkness and Donna Noble all together piloting the TARDIS back to its correct location. It's a magical moment to see all these great characters share screentime together; this many companions in the TARDIS at once had never been done before and hasn't been done since. There's a wonderful sense of joy; of excitement and wonder, like Russell T Davies unleashed his inner child and threw all his toys together out the toy box. This felt as much like a celebration of the Russell T Davies era as it did an epic conclusion to series 4.

As usual, David Tennant is on top form as the 10th Doctor and shows exactly why he is my favourite Doctor. His 'regeneration' is so convincing that you wonder if he will actually regenerate into the next Doctor rather than abort it somehow. Of course, he manages to divert it to remain 'The Doctor' but for a second you wonder if he will change. Oh, and Elisabeth Sladen yet again made me wish she'd stay on as companion. Billie Piper's second exit is sad if anticlimatic. Noel Clarke and Camille Coduri are the scene-stealers they always were during Russell T Davies' time as showrunner. Catherine Tate demonstrates exactly why many consider her to be among the best companion s with a tragic departure. Freema Ageyman is still the good thing about Martha, even if I don't totally like her character. Everybody is on top form, including Murray Gold who delivers some brilliant music as always.

Overall, The Stolen Earth/Journey's End proved shared universes worked before Marvel Studios (although I'm sure some will argue that Marvel did it within their comics) with a brilliantly barking mad comicbook-esque story that feels like an epic conclusion to Russell T Davies' last full series as showrunner.