After only four stories we have reached the end of The Third Doctor's first series - it continues to be a delight.

Inferno could have very easily been overly similar to The Ambassadors of Death, and indeed it began that way. If one criticism can be put towards Pertwee's first season, it is that they spend too much time inside corporate headquarters talking to business leaders / heads of projects. The key differentiating feature of Inferno is of course the parallel universe feature revealed at the beginning of Part Three which changes everything.

Variety is the essential nature of Doctor Who. What has worked with the back to basics approach to season seven is its stark contrast to what went before. However, in this story the audience is offered here is a journey into another dimension - a long awaited TARDIS trip which throws everything into the air. Once again, the change feels good, seeing the new Doctor in other worldly surroundings (even if they are parallel!) is an exciting novelty.

The regular cast appearing as evil versions of themselves is a brilliant concept. Brigade Leader Lethbridge-Stewart is running an alternate version of UNIT and expects answers from suddenly present Doctor. Section Leader Elizabeth Shaw is perhaps 10% more fierce than the character we are familiar with (joking).

The creatures in this story are spread by infection and rather than the familiar foam of Troughton's time, this is spread by a green goo. The infection idea is another very distinct concept for a monster, something this season has excelled at. In terms of the monsters themselves its half and half. As the initial stages of the Primord infection begin to take hold, they look brilliant, uncanny and dangerous. However, when the Primords go 'full werewolf' they look a little more dodgy (I was longing for a return of those Silurian masks). The consistent use of conveniently placed fire extinguishers to deter them is also tiring, but this is the plague of having to fill a seven part story. Shout out to plagued Benton though!

Once The Doctor has convinced the alternate versions of the various characters that they are doomed he somehow gets them to stop thinking about their impending death and begin preserving this newly introduced 'other version' of their universe. It is interesting to see The Doctor vacate a version of events in which everyone present is destroyed. Nicholas Courtney is wonderful as the cowardly Brigade Leader here, he is relishing this opportunity.

One of the preferable things about our version of events is the wonderful character of Sir Keith Gold who unlike his parallel self has survived. Its rare to get a bit part in Doctor Who which stands out like that. He of course helps The Doctor save his version of events.

The Doctor unsuccessfully attempts to leave in his TARDIS, so we are still on Earth for a while yet. Inferno has given me a taste for what is to come. I want more of Pertwee is space.

I'm still not sure what to make of Liz Shaw. I love the actor, but I feel like the character has been positioned somewhere in between Benton and the Brigadier. She is more of a UNIT member than a companion, which is odd. I don't feel like I have ever properly felt that spark between her and The Doctor, which is a shame as there are so many intriguing aspects to her performance. She is certainly not bland and we have had much worse! This feeling of liking but not loving makes this a difficult final outing. I feel like I want to see more, I want to see her character develop.