It's been three quarters of a year now since the BBC screened the third series of Torchwood, Children Of Earth, across five subsequent nights last summer. It was a sizeable gamble for the show, too, which was transferring to BBC One for the first time. John Barrowman, at the time, argued that the price for switching to One was that the series was truncated down to five episodes in total, but the decision to screen them all across five days was a bold one. Especially for a science fiction show that many still regarded as a Doctor Who spin-off with swearing and stuff in it.

That week last year, though, made for some exhilarating television, and also saw the team behind Torchwood lift the show to its highest levels to date. It was an utterly compelling five nights of drama that proved to be a sizeable critical and commercial success. So much so that more shows have now been scheduled in the same way since. You can put part of the that down to Children Of Earth.

It can't have been just us though that, even appreciating we were in the middle of a year of massive cost cutting, thought the fourth series of Torchwood was a foregone conclusion. After all, what more did the show need to do? It'd dragged millions of viewers to the BBC in the midst of summer, it'd sold lots of DVDs, and it had answers to many questions about how dark the show could go without losing an audience.

Even if you were one of the Children Of Earth dissenters, it was surely nonetheless refreshing to see a show of its ilk and content - and that penultimate episode remains burned into our retinas - on BBC One on a weekday evening.

But since then, there's been no sign of a new series being put into production. We've had rumours, quotes and signs of life, but nothing definite.

Russell T Davies said even before Children Of Earth screened that he had plans for a full fourth series of Torchwood, whether it was for a five or 13 episode run. He declared at the time that it was dependent on the performance of Children Of Earth. We come back to the question therefore: what else did it need to do?

As late as November last year, Davies was reportedly suggesting - although he never confirmed this - that Torchwood's fourth series was in the works, and that things were due to start moving on that in January 2010. I attended a Q&A with Davies in December, though, and he wasn't really saying anything of the sort then. Instead, he was repeating the line that, in spite of what John Barrowman had been saying, there was no firm news on more Torchwood.

Barrowman has been quite vocal about it, as you might expect. He said towards the end of last year that he's signed up for a deal to do a 13-episode series four of the show (and BBC America too had hinted a new series was on the way), but again, all official sources downplayed this.

Could it be that Torchwood had arrived looking for a recommission at just the wrong time? It's been well reported that the BBC is looking to end some of its longer running dramas - Spooks is in line for the chop, for instance - in favour of bringing in fresh series instead. Is Torchwood ultimately a victim of that policy? It's unlikely, given that the BBC is investing heavily in drama from its Cardiff base, but it may still have caused delays at least. After all, Davies had said that the outline for the series was pretty much in place, so you have to assume that it;s the BBC that's been reluctant, for whatever reason, to pull the trigger.

Maybe the biggest spanner in the works is Davies himself, though. He's moved to America since he finished work on the Doctor Who specials of last year, and is said to be writing some projects for US TV as a result. That, in itself, doesn't rule out him getting involved with a UK-set Torchwood, of course. Two more series of The Sarah Jane Adventures have been commissioned, and Davies is on board as executive producer. The BBC has just hired in another producer, presumably to take day-to-day running duties.

Distance, therefore, shouldn't be a barrier to a new Torchwood series. But what could be is interest from the Fox network in the States about developing a US version.

Fox has burned through a few sci-fi shows in recent years - Dollhouse and The Sarah Connor Chronicles, anyone? - yet, it still retains an interest in the genre.

Thus, in January of this year, it was reported that Fox was keen to develop a US Torchwood that would have Russell T Davies on writing duties. Were that true, you could understand that that's where Davies' focus would be (it would suit perfectly too, given that he's in Los Angeles). It would also involve John Barrowman, hinting at some continuity with the British version (Barrowman has, after all, turned up in Desperate Housewives, so US executives are likely to be warm to the idea of him returning).

Were Davies to press ahead with that, and it's looking possible, then you'd have to assume that the BBC Torchwood show would be mothballed for the foreseeable future, if not forever. Depending on the success Fox has or otherwise with it, it would after all  eat up the time and energies of Davies and his close team.

The last we heard on all of this was John Barrowman turning up on Radio 2 over the weekend. For a change, Barrowman was quite coy on Torchwood's future, reiterating that he'd love to play Captain Jack Harkness again, but adding that he wouldn't mind whether that's in the UK or the US.

Given that John Barrowman has hardly been shy about revealing Torchwood information in the past, we wonder if this hints heavily at the US version gaining traction? After all, the world of US TV tends to be a more secretive place, and the actor is likely to have to toe a PR line more heavily in the US than the UK.

Whichever direction Torchwood is heading, further news would be welcome very soon. The momentum of Children Of Earth may have been diluted, but it's still a series that's stayed long in the memory of some of us who sat through it. It also reignited a thirst for more Torchwood that it'd surely be folly not to capitalise on. Our best guess is that the American version takes precedence, and thus we wait to hear news on that.

Sooner rather than later though, please?