In another life I write about cars. And people ask me about cars. Why do they all look the same? And the answer is this: The reason all cars look the same is the same reason all Doctor Who seems the same these days.
Any car that goes on sale in the UK in 2014 must conform to a series of laws. Laws of safety, laws of aesthetics, laws of physics. That means that - at every point in the design process - certain facts must be accommodated. Bonnets must be shaped a certain way to mitigate pedestrian injury in the event of a collision. Side panels must be flared because all side panels are flared. And cars must adhere to certain shapes and sizes to offset aerodynamic drag that affects slippiness, fuel economy, speed and handling. By the time you've factored all that stuff in, you haven't got much room to play with.
I first thought that the 45-minute episode format was the most constrictive rule that new writers had to adhere to - there only so many ways you can set up a story, explore it, throw in the inevitable bait-and-switch, wrap thing up and have time for a coda in which the companion throws a hissy fit, the Big Bad has a surprise cameo or the Doctor unfurls one of his voluminous speeches.
Personally I think this is becoming more telling and even the self-consciously hyper-compressed episodes we've had from Season 7 onwards hasn't really changed the dynamic. You either have a very small, self-contained story or you have a breakneck episode that must sacrifice coherence for the running time. And while I didn't think many two-parters worked out, In The Forest of the Night could have done with some room to breath.
But I think there's another factor that's affecting Doctor Who at the moment - that factor is Steven Moffat. Frank Cottrell Boyce's episode promised great things. The set-up is quite wonderful - it put me in mind of Jim Mortimore's rather good New Adventure Blood Heat - and the promise of a rather lyrical, enigmatic story from a writer much admired was mouth-watering.
How disappointing then to see this wonderful premise progress along such familiar lines. Talking to the whole planet on a mobile phone, children being behind everything, some more of Danny and Clara's weird relationship dynamic, another 'silly old Doctor, of course!' realisation that concludes the episode, the huge lack of threat, a foe that wasn't a foe, some rather poor child actors, Murray Gold...
It really doesn't have to be like this. I have no doubt that Cottrell Boyce could fashion a beautiful novel from that same premise, but In The Forest Of The Night was the least engaging episode of the season thus far, in a season's worth of unengaging stories. All that promise - eyes in the darkness, the forest metaphor, monsters, an alternate London was suffocated under a ream of Moffat tropes.
While the writer was confident enough to do away with the Sonic Screwdriver, there were still mobile phone and mountain bikes and marking and newsreaders and TARDIS scenes. Elements that drag the concept back to a modern-day milieu that is the series' touchstone - as if we couldn't possibly relate to The Doctor without these everyday objects and settings.
On a more perfunctory level, the amount of mawkish sentiment hit new heights this week. That "Daddy, my Daddy" scene in The Railway Children has cast a long shadow over writers in search of a shortcut to emotion over the last 40 years and the incredibly clumsy 'missing child found under bush' scene was a genuine low point in the series.
Capaldi shines as ever and there are some nice directorial touches but this series is back to a parlous state after two strong episodes. Aside from a slight return in the second half of Season 7, Doctor Who has not been in rude health since Matt Smith first took the TARDIS controls back in 2010. And while companions, Doctors, producers and execs have moved on since, there is one common denominator to these underwhelming seasons.
Gatiss and Roberts seem to have given up on delivering anything outside their usual self-pastiches but when even the likes of Cottrell Boyce and Neil Gaiman seem unable to drag the series away from its cosy middle-ground, you have to wonder whether the series can ever thrive under such self-imposed strictures. Every story now seems Moffat-lite, as if the series can't escape his own personal gravity. You can't change the laws of physics and Doctor Who needs a rocket escape the fearful aerodynamic drag of Steven Moffat's tired vision for Doctor Who.