Doctor Who: Every Modern Companion's DEFINITIVE Episode

There was no other choice here - this is the mission statement for Donna as a character. Turn Left is a character study of Donna Noble, stripping the Doctor and his influence away entirely. On the surface this story looks like your bog-standard alternate timeline story, a 'what if Donna never met the Doctor', but that isn't the point. The show has laboured the point of Donna being made better by The Doctor, but this story shows us that everything the Doctor bought out in her was there all along, with or without his guidance. 

This is a version of Donna who never left Chiswick, one that remains exactly as we first met her in The Runaway Bride, trapped in an unexciting life and stifled by a demeaning mother, but there are also echoes of the Donna she grows into - her inherent humanity and heroism shining through, filtered through her slightly abrasive exterior. Even without the Doctor, the Donna we know and love is still in there, she's just too guarded and worn down to let it come to the surface. 

At the same time, the episode also allows us to see what Donna might have been like before the Doctor, spending an extended period of time with her as she just tries to live her life as the world collapses around her. Her lack of purpose and drive becomes more prominent, her relationship with Sylvia is colder and even more strained, and she harbours a general resentment for the world and everyone in it. Wilf, by contrast, is still an absolute gem and a saint, and his bond with Donna in this world is the only thing that anchors her. 

We can see in this story that traits we often associate with Donna (her humour and quickness to anger) aren't just kooky traits, but tools she uses for survival and self preservation. The humour is still there, but it's more biting and harsh, you can feel her sense of desperation and helplessness through her every action. It's a subtle change, but it's a perfect showcase of exactly what Catherine Tate blew us away with in 2008. For someone who honed themselves in comedy, I genuinely think Catherine Tate is one of the best dramatic actors to ever take on the role of a companion in this show, and there is no better showcase for her talent than this episode. 

Much like Human Nature is a story about the Doctor 'without' the Doctor, Turn Left isn't really about an alternate timeline Donna, it's actual purpose is to reveal that the 'ordinary' Donna is anything but ordinary.