For whatever reason it’s come about, be it as John Barrowman suggests: the BBC “punishing” Torchwood for its success, or rather the desire to create a five episode event over one week, there can surely be little doubt now that Torchwood: Children Of Earth has been an immense success. With ratings continuing to hold strongly after an impressive opening audience figure, the momentum of running five consecutive episodes has really paid off, and with some style.

But what’s really set Torchwood apart here is its willingness to take some major, major gambles. We saw it at the end of season two, when two of the crew were disposed of. And last night? We saw the demise of Ianto, a genuinely shocking moment, where a television show took one of its most popular characters (and arguably its most popular character full stop), and had him killed off just so the sinister 456 could prove a point. No big dramatic fall, no going down in a hail of bullets. They just, well, killed him. It was jaw-dropping risk-taking, and a move that’s already led to protests from fans, and many questioning whether a fourth season of Torchwood could go ahead with one of its vital organs ripped out.

The thing is, though, there seems little evidence from the four episodes thus far that Russell T Davies is even looking towards a fourth series here. This has been a compelling and relentless exercise that’s seen the Torchwood hub blown up, and the core team reduced to two. Personally, and I’m saying this knowing no spoilers or rumours, I don’t fancy Gwen’s chances of seeing through tonight at this rate, as Torchwood has proven that nobody’s place – unless you happen to be invincible – is safe anymore.

And that, despite the protests about Ianto’s death, has to be a good thing. It harks back to something like Blake’s 7, where the core thrust of the show remained, even if the crew kept changing. With Torchwood, it’s good that a popular character can die, and my big hope for tonight is that it doesn’t bottle it and find a way for Ianto to come back to life. Granted, that’s not going to make me very popular amongst some, but this is a show that’s demonstrated the courage of its convictions, and back tracking on that is a non-starter for me. Ianto has to stay dead, and not be resurrected in a Doctor Who-alike way.

Also, I’m hoping that Russell T Davies will keep the 456 in the shadows for the whole five-episode run. They have been a genuinely unnerving foe for the world to face, primarily because we’ve not really seen them, nor have any idea of just how tangible the broader threat from them is (apart from a general feeling that we’re all well in the shit). That’s just the way it should be, and to get so far without putting a face to a threat – instead allowing the writing to explore that humanity is actually its own worst enemy – has been a simple choice, executed expertly.

If there’s one slight fear here, it’s that Russell T Davies has left himself a fair amount of wrapping up work to do, and that penultimate episodes of his shows tend to be better than the finales themselves. But he’s stacked his cards firmly in his favour here, and if he holds his nerve – as I suspect he will – then there’s no reason why Children Of Earth can’t finish the job off as expertly as it’s started it.

How much it leaves things for a fourth series is uncertain. We reported recently that a fourth season is all ready to go, should the ratings for Children Of Earth be good enough. And it’s fair to say that the show has proven to be a significant success in its summer schedules for the BBC. It’s likely to have brought more viewers through the door longer term, and has set things up for further week-long event series in the future too (which, as Dead Set proved last year, can be a terrific way to go). In short, it’s hard to see – if ratings and critical reaction are the criteria – how the BBC could say no.

But then it depends just what state everyone is left in at the end of Children Of Earth. One way or another, there’s got to be a recruitment drive, with prime candidates being Lois and perhaps, at a push, Rhys (although that’s dependent on what happens to Gwen, of course). The only constant right now? That’s John Barrowman as Jack, and I wouldn’t rule out a rug pull there, either.

In the midst of our review of episode four of the show, we added a plea for the Torchwood crew to please not blow it now. Because this has been compelling, exciting television, and a series that deserves an ending as good as the built up. Our gut feeling? We may just get it.

Either way, our review will, touch wood, be up as soon as possible after the finale airs, depending on just what state we're left in come the end of Children Of Earth.