Having prematurely washed my hands of this latest series of Torchwood (at least in print), it seems only fair that I should redress the balance.  So let’s go on record to say that after a shaky first episode, Children of Earth actually turned into everything I never expected Torchwood to be – an excellent Quatermass Conclusion­-inspired thriller.

While many of the series’ perennial problems with characterisation and performance remained (after three series Jack Harkness still works better as a supporting character in Doctor Who than a lead in his own show), here was at last an alien invasion plotline that felt appropriately epic and significant.  Perhaps it helped that this storyline didn’t require any unconvincing FX shots of aliens storming the Eiffel Tower or Taj Mahal, instead the invasion was neatly kept at the conceptual level.

Having dealt with the business of dismantling Torchwood – and indeed Torchwood - as we know it, the remaining four episodes in this mini series were free to delve deep (perhaps deeper than we have ever previously seen in the Doctor Who universe) into the difficult politics of “greater goods” and impossible decision-making, revelling in protocol and pseudo-authentic sounding bureaucratic speak.  Perhaps the highlight of the whole week was the protracted sequence in which the cabinet sat around discussing the most appropriate selection criteria by which they could choose their sacrificial 10% of the world’s youth population.  This was utterly gripping, not just because of the impossibility of the task, but for the amount of screen time the debate was allowed to eat up – for a moment there Torchwood came to resemble a superior stage play in which a great moralistic issues is scrupulously weighed and examined, each protagonist adopting a different intellectual position and locking horns with one another.

The portrayal of the “456″ was equally well measured and balanced.  As a viewer we instinctively knew their effect would be all the more menacing if they remained enigmatic.  Strange tentacles aside, it was to the production’s credit that we never actually got a proper look at them.  Nor did we ever get a handle on where they came from, or their wider motivation, beyond looking for their next hit.  Being denied any understanding of the 456′s psychology kept us all on our toes.

Let’s be clear, so good was this series that for once it didn’t seem to matter that Captain Jack’s initial plan to vanquish the 456 consisted of nothing more than telling them to sling their hook, nor did we really care that any organisation sufficiently advanced to create spy camera contact lenses would surely be able to come up with a sufficiently undetectable microphone.  Set against a properly serious and ambitious story that put its characters into genuinely difficult physical and moral situations, any objections to Peter Capaldi’s somehow unrealistic looking attire couldn’t help but melt away.

While Doctor Who has shown there is a way to do science fiction on telly that will appeal to a mass audience, Torchwood: Children of Earth showed us that with the right storyline and the right schedule, you can lead a mass audience into an appreciation of the kind of serious television sci-fi that many thought lost since the heyday of Nigel Kneale.  Now that’s a shock ending.