I'm going to struggle to properly assess "The Poison Sky" for reasons I'll explain in just a moment, so instead I'll look at other peoples criticisms of it and see if they hold any merit. That I enjoyed the episode hugely is a surprise, given that it was beginning only as I plonked my seat down on the floor with seconds to spare. Yes, how ironic that while the Doctor was hampered on screen by Evil Sat Nav, my path to the episode was impeded by the lack of one, as I swung off two wrong junctions, ended up closer to Leatherhead than my intended destination, and for the second time in my life, blew into someone else's living room to catch the start of a new Doctor Who episode with less than four minutes to spare. From the mighty "Now" perspective, as things stood at 6.20pm on Saturday, this episode came over as a mighty success, and ironically very appropriate for a sunny May evening, as on-screen the Doctor and UNIT battled hoards of Sontarans in an equally blooming clime.

So, peoples gripes! (as I had, and at this time have, none to speak of). We can overlook the usual small picky things - the Sontarans were too short to be menacing, Luke Rattigan's Terraforming Gun was a bit convenient, the Earth being ignited business wasn't scientifically much cop, Martha wasn't very good at being a Doctor when her clone was dying... these are peripheral moans. Writing a water-tight story is difficult, but not always essential anyway. It's true, that when there are so many leaks, the whole can wind up a flood of glitches ("Timelash" for example), but to a certain extent, small plot inconsistencies come second to enjoyable set pieces (like the truly amazing CGI effects in this episode - the Sontaran ship and the stunning realisation of Earth being engulfed in flame). It's not that spectacle covers over poor plotting - just that you don't always NEED to obsessively cover every small thing that someone, somewhere might pick apart. Even real life doesn't make complete sense sometimes, and it's doubtful how many excitable viewers would really be that bothered if someone pointed out afterwards that Rattigan's mythical New Earth seemed to have been added in simply to provide a denouement. Who really cares, when it was all this thrilling?

But there is another, more sombre complaint made about the show these days - and it's a point suited to being addressed for this episode - and that's that Doctor Who has got predictable. The show that once pushed the envelope, and did things contrary to anything else happening on TV, can now be foreseen in advance with depressing accuracy, we're told. If I told you that my favourite season was one where the Doctor meets a new companion in Episode 1, introduces her to history in the subsequent adventures, fights off an alien threat to contemporary Earth later on while being browbeaten by her Mother, picks up a second, more short-lived assistant mid-run before winding up with a sky full of alien killing machines and a threat to, well, EVERYTHING in the closing weeks... would you really know which of three (possibly soon four) seasons I was talking about?

But I don't really agree with this as a criticism, simply because... well, why shouldn't Doctor Who follow a formulae these days? Other hitherto untried conceits (self-contained stories, semi-regulars, returning companions) have been a success since the series returned. The production team have successfully been lead by what works in television today, rather than the rules the old (fifteen year old series) slavishly followed, and this is particularly important when you consider the story-arc led trends of sci-fi in the nineties and beyond. There's also a difference between following a broad pattern and repeating yourself. It's not as if the same enemies or plot ideas are being re-used each year - it was only the continuous serial nature of Old Doctor Who that stopped them having a definable shape to each season anyway. Featuring a celebrity historical in the early stages and a minor linking element each year is repeating a practically sensible idea, not wearing out a creative one.

That said, perhaps they are ideas without INFINITE mileage. I don't know when the time for brave change is, but when the series returns in 2010, it would be nice if things changed a little. If there wasn't a big spectacular Universe-threatening climax to every season, and if there weren't still little visual nods to the climax peppering the early episodes. Just because our series has *always* ultimately thrived on change, and radically re-booting itself. It'd be nice if that was one change which wasn't lost in its twenty first century incarnation.

For now though, there was nothing, for me, tedious or predictable about "The Poison Sky" - a fresh, boisterous, well-made Doctor Who episode if ever there was one. Now how about an adventure set in Peru?

Si.