This episode is extremely underrated, I hadn't watched it since it came out and upon rewatch I was shocked at how good it was! It has everything I like, I love a horror themed episode set in space.

The scariest monster in all 60 years of this show. Capitalism.

Now here's a story I loved on first watch, and only grew on me with time. Oxygen is a real gem, and I've been glad to see it getting some more serious attention and appraisal in the years since its broadcast.

One of the things that makes this story so unique is its uncompromisingly "realistic" take on space travel. Rather than some sort of cosmic ocean, here we see the vacuum as an antagonist in and of itself, even if an unconscious one, and are reminded of the fragility of human existence, hugging the skin of our blue planet. The frozen corpses throughout this episode are really grim stuff, especially for Doctor Who, but used so well that it never comes across as gauche.

And there's the political angle, of course. This is probably the most uncompromisingly anti-capitalist story in Doctor Who's history (with perhaps The Sunmakers as the only exception, as in this one they just give the bosses an earful instead of chucking them off a building). Capitalism, like the vacuum, is presented here as an impersonal force that's utterly inimical to human life. The difference, in the end, is that capitalism was created by humans, and so it can actually be vanquished.

That aside, Bill and the Doctor are both fantastic in this one, between the Doctor's blindness (and what a twist at the end!) and poor Bill grappling with what seems to be her most dangerous adventure yet at this point. I was biting my nails over the scene where she appears to get electrocuted by her suit, back when I first watched this.

An incredibly cold, scary, isolated story - and with a nice message to boot. It's one of my favorites of its era.

Many are describing Jamie Mathieson as the Moffat era's Steven Moffat, and it's not hard to see why. Whilst none of his episodes have particularly scared me in the same way Moffat's have, Jamie Mathieson's stories for the show mainly tend to lean towards the darker corners of the Whoniverse. This probably makes him the closest to what Russell T Davies had with Steven Moffat as a one-off writer. After Series 9's more light-hearted The Girl Who Died, oxygen is another dark episode from Mathieson in the vein of his series eight stories.

In Oxygen, The Doctor (Peter Capaldi), Bill (Pearl Mackie) and Nardole (Matt Lucas) arrive on the space station Chasm Forge in the far future, where oxygen is sold by businesses as a commodity. The Chasm Forge crew are supplied oxygen through their space suits, programmed to give oxygen in relation to how many credits the wearer has. Things are not as they seem as the TARDIS crew discover some of the crew onboard the Chasm Forge are dead, and still walking. The suits have been killing their occupants, but is it the result of the suits' Artificial Intelligence going rogue, or has someone programmed them to do it?

The episode gets off to a slow start, but once the plot kicks into gear it proves to be a thrilling episode. The Suits prove for very effective monsters, essentially like space versions of zombies. Doctor Who has of course played with zombies before - most notably in 2005's The Unquiet Dead - but the monsters featured here are probably the most obvious examples of zombies in the show so far, and perhaps the most interesting take.

The idea of suits trying to kill their occupants is a very unique one, especially with the combination of the very Douglas Adams-esque idea of businesses selling oxygen. Some viewers may not like the very prominent anti-capitalism message in this episode, but I think it's one that is extremely relevant to today's society. The other day I read an online article about the Scarborough Council charging people 40p to use public toilets, and this is something that I believe is a disgusting money-making exercise. Why should you have to pay to go to the toilet? Why should you have to pay for oxygen? The two are instantly comparable, and charging for public toilets essentially turns councils into businesses.

Two things are very impressive about the production of this episode. The first is the make-up of the space zombies. The space zombies look fantastic, and pretty much as convincing as those you see in high-profile movies featuring zombies such as Shaun of the Dead. The second is cinematography. There is a brilliant sequence in this episode where Bill is exposed to the vacuum of space without a space helmet, and the image blurs and distorts to show the effects of the exposure. It's such a clever and well-executed sequence, and one that deserves recognition for how immediately effective it is.

It's the aftermath of the vacuum sequence with Bill that also highlights how much the 12th Doctor's characterisation has developed throughout his era. Series 8 Capaldi wouldn't have cared less that his companion was being exposed to the vacuum of space, but Series 10 Capaldi saves Bill by giving her his helmet. This results in him becoming blind, meaning we have our first disabled Doctor. Quite how this will play out in future episodes is a mystery, although it seems likely that his eye sight will be fixed when he starts to regenerate in the Truth Monks three parter. It's a bold move by Moffat and one that should be applauded.

We are led to believe before the final scene that the Doctor's blindness was cured in the TARDIS, but in the final moments it is revealed that he is still blind. The way this was revealed didn't quite work for me. It was made a little too obvious in the scene by the way The Doctor is suddenly wearing his Sonic Shades again and not looking directly at Bill and Nardole when they are talking to him. It also feels like a cliffhanger for the sake of having a cliffhanger. Why bother showing a scene in the TARDIS where it looks like he's been cured? Why not just end with the blind Doctor and companions leaving in the TARDIS for the Doctor's office at St Luke's University?

If the cliffhanger didn't quite work, this episode did deliver in another area. In Oxygen, we finally get to see more of Nardole. This time his appearance isn't a brief cameo at the beginning or end of the episode, but as a proper companion to The Doctor like Bill. Finally I can form some sort of opinion on the character, and so far I like him. He's a fun companion for The Twelfth Doctor, and displays some interesting chemistry with Pearl Mackie. I can't wait to see more of his character in Extremis; hopefully he isn't relegated to cameo status again, as I think there's potential yet to be realised with Nardole.

Overall, Oxygen starts off slow but once it gets going it proves to be another great episode from Jamie Mathieson. The space zombies are very effective, and the central premise is reminiscent of Douglas Adams. Also: Matt Lucas is finally featured in more than just a brief cameo! Unfortunately the game-changing cliffhanger is made a little too obvious in the final scene, and if you pay attention to the way Peter Capaldi plays it you will figure out what the cliffhanger is straight away.

Oxygen has a lot of great ideas and elements that make for solid science fiction.  The premise is simple enough but feels all too plausible in a fundamentally capitalist space-faring society.  The story gets a little weak and self-indulgent in a way only Moffat can be at the end, with the Doctor almost brushing aside capitalism with a few simple moves and suddenly going blind.  That stuff feels a little forced and silly in an otherwise tight and menacing experience.  Either way, in spite of some faults this was a solid experience and a great example of Doctor Who using politics pretty well - Capaldi gets to be a real punk-rock badass in this story and Bill really goes through it here.