So the first two parter arrives for series 4, once again aliens are trying to take over the world using everyday objects, like most of Doctor episodes (bluetooth used in series' 2's cyberman two parter) - this time it's the turn of the Sat-Nav system, called Atmos - which has unexpicably killed 50 odd people around the world at exactly the same time.

Martha who is working for UNIT - as seen in Torchwood - calls the Doctor in to help. Atmos has been developed by a young genius who is actually in league with the Strontaran, a warrior race who live for war - and just look like giant pototoe heads!

Martha's introduction is a little clunky "Doctor I'm bring you home" eh? couldn't they come up with something a little smarter? Actually for the most part Martha comes across rather stiff throughout the episode, making Donna seem even more likeable as the doctor's current companion (whether this was a ploy to make us like Donna more, well we'll never know..). She seem's to be thrown in as some sort of afterthought, hopefully the same will not happen to Rose when she reappears in the end of the series?

David Tennant is on fine form this week, his portrayal of the slightly eccentric genius doctor is spot on, especially after last week's rather subdued performance. If nothing else, this episode spotlights him and makes us all realise what he brings to the role.

The return of the Strontaran, is a slow affair, we are gradually shown them over the course of the episode, although in reality we are only shown two of them without their heads on. The performance is fine, with the effect of Aristocracy becoming war faring aliens working well.

The plot is really stretched thin this week though, seems a lot of bother just to gas the planet by fitting in the SatNav pollution reducing Atmos - perhaps convulted plots are part of the attraction of Doctor Who, and simply invading aliens would be, or would get boring after a while (which kind of makes sense I guess) - The only problem I have with the Strontaran is that they look like "comedy aliens" like the ones from series 1 - however we can't have all the Aliens like Daleks and Cybermen I guess - would be nice to see some new Aliens that aren't part of Doctor Who canon being introduced.

The episode overall, seem a little dragged out - but I suppose this is just the setup of the next episode - since nothing really happens until the last 10 minutes. I didn't squirm my way through this episode like I normally do on two-parters, and acually felt entertained while I watched it.

Lets just hope unlike last years effort, we are not dissapointed by the second part...

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