• Another Life
• Border Princes
• Slow Decay
• Something in the Water
• Trace Memory
• The Twilight Streets
• Pack Animals
• Skypoint
• Almost Perfect
• Into the Silence
• The House That Jack Built
• Bay of the Dead

• Hidden
• Everyone Says Hello
• In the Shadows
• The Sin Eaters

Torchwood began on BBC Three in October 2006, and was the first spin-off from Doctor Who to get beyond the pilot stage — the only other attempt being K9 and Company in 1981.

Aimed at an adult audience (unlike Doctor Who which is targeted at a family audience) the series features the secret Torchwood organisation who, by the time of the opening episode Everything Changes, are firmly based in Cardiff after the destruction of their main headquarters at Canary Wharf in London after the epic battle between the Daleks and the Cybermen in the Doctor Who episode Doomsday.

And the reason for their existence? To investigate anything out of the ordinary and to purloin alien technology for the benefit of Great Britain.

In charge is Captain Jack Harkness (John Barrowman), former TARDIS traveller and intergalactic con-man who has been stranded on Earth since the events of the Doctor Who episode The Parting of the Ways — although an explanation for how he actually came to be on Earth wouldn't be forthcoming until the Doctor Who episode Utopia, in June 2007, when he temporarily rejoined the parent show.

The opening episode, Everything Changes, saw police officer Gwen Cooper (Eve Myles) becoming entangled with one of Torchwood's investigations and subsequently being asked to join the organisation. Other regular characters were Owen Harper (Burn Gorman) — Torchwood's resident jack-the-lad and medic; Toshiko Sato (Naoki Mori), Torchwood's technical wizard, who first appeared in the Doctor Who episode Aliens of London); and Ianto Jones (Gareth David-Lloyd), the general dogsbody and organiser.

Initial reports on Torchwood during production suggested "dark" and "sexy" as being the keywords to the series, which was intended from the outset as a post-watershed science fiction series for adults. Sadly, something went wrong along the way as, like BBC One's Robin Hood, the series spent much of its opening season trying to find its feet, with only a handful of episodes being even remotely up to scratch. And the only ways in which the stories could be said to be remotely "adult" in tone was the swearing and sex which were shoehorned in with precisely zero subtlety whatsoever.

Standouts in the rather tiresome first season included PJ Hammond's fairy-infested Small Worlds, and Catherine Tregenna's Out of Time, although even the latter was heavily indebted to the Season 1 Star Trek: The Next Generation episode The Neutral Zone. Those to be avoided were generally written by Chris Chibnall, including such televisual travesties as Cyberwoman and the gore-filled Countrycide.

Despite the generally poor standard of the scripts, the series attracted an incredibly healthy audience for BBC Three, blowing away viewing records for digital-only channels as it went along, and a second season was swiftly commissioned. Mercifully, with the exception of the opening episode, Kiss Kiss, Bang Bang, the stories were generally more in keeping with the better episodes from Season 1, with Doctor Who's Martha Jones (Freema Agyeman) arriving at Torchwood for a three-episode stint in the middle of the season.

With the demise of both Owen and Toshiko at the conclusion of Season 2, it was apparent that when the series eventually returned to the screen it would be with a number of changes. However, before Season 3 could be formally announced, it was revealed that a one-off radio episode, written by Joseph Lidster and set after the conclusion of Season 2, would be broadcast on BBC Radio 4 to tie-in with the switching on of the new Large Hadron Collider particle accelerator in Switzerland. Also on the cards was an appearance by the surviving Torchwood members in The Stolen Earth and Journey's End, the concluding episodes of 2008's season of Doctor Who.

But before the two Doctor Who episodes were broadcast, it was announced that Season 3 of Torchwood would consist of a single five-part story titled Children of Earth, and that the series would be promoted to BBC One and stripped across a single week.

Early 2009 saw the announcement of three new Torchwood radio plays for broadcast on BBC Radio 4, with the intention that they would be aired as a lead-in to the year's big television event. They were eventually to turn up just a week before Children of Earth arrived on screens, spread over the space of three consecutive days in the Afternoon Play slot.

Children of Earth itself was finally aired amid a blaze of publicity between 6 and 10 July at 9pm, and saw a species known as the 456 arriving in Britain and secretly demanding ten percent of the world's children. With the government eager to ensure that details of an earlier visit were kept quiet, Jack, Ianto, Gwen and her husband Rhys soon found themselves on the run and trying to deal with the alien menace whilst staying one step ahead of a government hit squad who had already destroyed the Hub in Cardiff in an attempt to permanently wipe out Torchwood.

Unusually for a serial, Children of Earth's ratings actually increased as the week progressed rather than dropping off, finally bowing out with 6.58M viewers, who saw Jack sacrificing his grandson, Steven, to save the rest of the ten percent who had been rounded up by armies around the globe under a cloak of secrecy, led by UNIT. Along the way the story also saw the death of Ianto Jones, leaving Jack and Gwen as the only survivors of Torchwood Cardiff.

With Captain Jack Harkness leaving Earth at the conclusion of the story, the series would at first glance appear to have run its course. But with its extraordinary summer ratings, it would be foolish to think that the schedulers would be ready to let Torchwood end just quite yet...