This story is not only matches Terry Nation's initial two Doctor Who efforts, it outshines them and reinvigorates the Daleks, who in my opinion had become stale by this point.

This story has a real purpose and vision which Nation's work had lacked for quite some time. The outgoing Barry Letts and Terrance Dicks had placed higher expectations on Nation after being displeased with his initial same-y script for this 6 parter. Incoming Philip Hinchcliffe and Robert Holmes then helped further develop this into something dark, new and exciting. The efforts of all five of them can be felt here. I can't think of a better Doctor Who story up until this point.

Darkness is not a flavour which I believe is at the core of Doctor Who, but I think that one or two stories a season can be justifiably darker in tone than the rest. After the romps of Robot/The Sontaran Experiment and the comedic The Ark in Space - there is certainly room for discussions of pure evil and genocide. Moments of hope run through this story before being dashed each time, in a show where we are used to The Doctor always winning - this has a powerful effect on the viewer.

The pacing of this story is notably fast, which is very rare for a six part story. From the first scene we are thrown into the action - The Doctor is sent on a mission to Skaro by the Time Lords' only to find out that he is already on Skaro. Skaro is home to three races: Thals, Kaleds and (new to this story) Mutos which gives The Doctor and his companions a huge wealth of characters and cultures to explore.

One could dub this story "Doctor Who and the Nazis" as no effort is made to hide the influence of WWII on this story, it is very effective. Kaleds are presented as wartime Germans but pleasingly there is nuance to their race. Many of the Kaleds find Davros' rise in popularity worrying and his beliefs abhorrent. The fact that the Daleks win makes this a cautionary tale - if good people are unable to make enough of a difference evil can triumph. These themes could seem cliche, but the Nazi uniforms, salutes and ethos of the Kaled race make them a highly credible and relatable threat (even all these years after the war).

The simple idea to do a genesis story for the Daleks is inspired. Since The Three Doctors the show has been happy to explore its own mythology, but this takes it to a new level - filling in tantalising gaps and making the show's lore richer and more detailed.

Davros is the best new villain since the Daleks. He has a very definite personality distinguishing him from the likes of Mavec Chen, Tobias Vaughn or The Master. Davros not only has a thirst for power but a unique ideology. Over the course of his conversations with The Doctor we are given a detailed justification of why he would like to be responsible for the destruction of everything. It is to Nation's credit that Davros' logic does not come across as flimsy or cartoonish.

The Doctor: It's not the machines, it's the minds of the creatures inside them. Minds that you created. They are totally evil.

Davros: Evil? No. No, I will not accept that. They are conditioned simply to survive. They can survive only by becoming the dominant species. When all other life forms are suppressed, when the Daleks are the supreme rulers of the universe, then you will have peace. Wars will end. They are the power not of evil, but of good.

Davros is also set apart by his disconnection from the rest of his own Kaled race. He is happy to betray them to the Thals in order to destroy most life on Skaro in favour of his own new creations. Another astonishingly evil and memorable move Davros makes in this story is forcing The Doctor to describe all the Dalek's future defeats by torturing Sarah Jane and Harry, this is an ingenious concept fit for an arch villain.

At the same time Davros is presented as vain and arrogant, considering his word to always be correct and logical - even when most people think he is wrong. For example, he is confident in his belief that there is no life in the universe outside of Skaro. When the Daleks inevitably overthrow Davros he comes face to face with his own arrogance.

Tom Baker's "Have I the right?" scene might be the most celebrated in Doctor Who's history and it is worthy of this status. Sarah Jane is wonderful in this scene, telling The Doctor what any member of the audience would - that the Daleks must be wiped out. This scene highlights the very "weaknesses" of The Doctor that Davros mentions, he could never condone genocide of any kind, for any reason. I feel proud of The Doctor as a hero and role model here, his disgust of violence and willingness to give peace a chance is perhaps his most amiable and important trait.

Thank goodness that the production team decided to depict how the Daleks came to be, this could have been another run of the mill Dalek story but instead it changed the entire shape of the show.

This remarkable, groundbreaking and dark six-parter does not end with The Doctor stopping the Daleks, instead he hinders their development. I think that is only right given that this is canonically his greatest enemies' first adventure.