WARNING: CONTAINS SPOILERS FOR TORCHWOOD: CHILDREN OF EARTH

The five-episode run of Torchwood: Children Of Earth last week can surely be regarded as something of a triumph for all concerned. Positive ratings, genuine critical acclaim and a thirst for a fourth season - unless you happened to like Ianto a lot - seemed as good as a result as the Beeb could have got from where I'm sitting.

And as Cameron noted in his review of the final episode, it sets the stage up for Torchwood to become a greater show than the one it's spun out of. I say that as a devoted and dedicated Doctor Who fan, and one who's thoroughly enjoyed the direction that the new Who has gone in over the past five years. Yet nonetheless, there are some reasons that became apparent last week as to why Torchwood needn't live in Doctor Who's shadow.

I thought the final episode of Torchwood: Children Of Earth, if you can forgive the sudden haste with which everything was wrapped up (and how much would you have wagered that Russell T Davies would have tied up its story using some kind of transmitter in there somewhere?), was strong and chilling television. The moment where Frobisher walked into the bedroom of his children, closed the door and then we heard the shots was just outstanding and unexpected. That, for me, is what ‘adult' drama is about, not just increasing the amount of cussing and allowing space for the odd bonk because it's after the watershed. No, Torchwood: Children Of Earth genuinely had a grown-up theme, and grown-up storytelling behind it. The idea that the 456 were simply taking children to feed a drug habit was similarly outstanding, and brutal.

But then, without the framework of a series that's run for 46 years behind it, Torchwood has the freedom to do things that Doctor Who would never dare do, or at least hasn't been able to since the earlier days of the show. The death of Ianto was a case in point. I've followed some of the online reaction to this, with many threatening to boycott the show. The criticism of it that I don't get, though, were those who say Ianto's death was pointless. Yet surely that itself was the point? For once, we didn't have a huge build-up, leaks in the press, and then lots of whining afterwards. It was brutal, fairly sudden, and didn't have particularly major plot ramifications. It was, simply, hard-nosed, and it would have made a mockery of things should Russell T Davies had opted for the reset button.

It did make me think that it was a good job Twitter wasn't around when Adric blew up, though.

The bit that really got me, though, in the finale, the Frobisher incident aside, was the tortured eyes of Captain Jack. John Barrowman earned his acting stripes and then some here, and gone was the chipper chap who occasionally popped up in Doctor Who from time to time. His world around him was destroyed, and I fully expected - having been schooled on a lifetime of Who - that a way to save his grandson was coming. But it wasn't, and instead, Harkness did his duty in a horribly matter of fact way, that was ripping his soul out as he did it.

Because here's the thing. Doctor Who can threaten to do lots of these things, but Torchwood has the space to do them. That has pros and cons, clearly, and I've been more frustrated with than a fan of Torchwood until last week. Yet when its focus is so finely tuned, Torchwood can follow through on the threats.

I've said in the past that Russell T Davies has a brilliant ability to write set up stories, but I'm usually disappointed by their pay-off. Not here. And you can't help but wonder how much of that is down to Torchwood being a show he's been in control with from day one, in a time slot that allows him to push just a little harder than its parent show.

Right now, Doctor Who still reigns supreme here for me. But there were moments last week in Children Of Earth that were far better than many episodes of the new Who. And should Torchwood now push ahead with that fourth season - and it's got some work to do to jigsaw things together for starters - then Children Of Earth has both won the show a lot of new fans, and proven that if Russell T Davies and his writing team really want to take a few more risks, people will come...

Torchwood: Children Of Earth is out now on DVD and Blu-ray.