'Torchwood' is a spin off of the seminal British science fiction TV series, 'Doctor Who', and indeed their names are anagrams. However, unlike its precursor, which was primarily written for children, it has an adult, sexually explicit storyline. It is set on Earth, and based on the Torchwood Institute, a secret organisation whose mission is to protect the Earth from alien artefacts and incursions.

The series was created by Russell T Davies, an accomplished screen-writer who had successes with 'Queer as Folk' and 'Casanova' before persuading the BBC to let him revive Doctor Who - the venerable and popular family friendly science fiction series about a time-traveller that first aired in 1963 and had been paused after 1989 (with the exception of one feature length episode.)

Critics who said that Doctor Who was passé and could not succeed in a 21st century with so much competition in the science-fiction field were comprehensively proved wrong, with the series going on to win the 2006 BAFTA Award for Best Drama Series.

In the first series, first shown in 2005, The Doctor meets a charming confidence trickster in 1940's London who calls himself Captain Jack Harkness and wears RAF uniform. Harkness is a renegade Time Agent from the 51st Century. Harkness travels with the Doctor for a while and in the series climax achieves immortality.

A further series of the new Doctor Who was commissioned and aired in 2006. In its second episode The Doctor meets Queen Victoria in the wilds of 1879 Scotland, where they spend the night under alien attack at an estate called Torchwood. Realising her empire is also at risk from outside this world, The Queen creates an institute to be named Torchwood to protect it. In the series finale, The Doctor arrives at the Torchwood Institute in London in the present day. His Tardis time-ship is confiscated - 'what is alien is ours' he is told by Torchwood but during a cataclysmic battle between alien armies the Torchwood Institute is destroyed before the Doctor can defeat the invaders.

The first series of 'Torchwood' aired shortly afterwards in late 2006. The Torchwood Institute branch in Cardiff, Wales is headed by Captain Jack Harkness, still wearing his RAF greatcoat. A voice over the titles proclaims that Torchwood is 'separate from the government, outside the police, and beyond the United Nations'. Gwen Cooper is a young police officer who is co-opted into Torchwood, and she performs the role of our introduction to their strange life. The first two series episodes consisted of stand alone stories about the effect of alien artefacts and repelling alien incursions, but by the end Russell T Davies had grown tired of that format.

The third series was dramatically different. Instead of 13 weekly stand alone episodes, 'Children of Earth' was a mini-series of one hour episodes shown over five consecutive nights telling one powerful story during which the Cardiff headquarters of Torchwood was destroyed and all its operatives were killed, except for Gwen Cooper and Captain Jack who went into hiding.

Shown after the 9pm watershed, where adult programmes are allowed, we found that Captain Jack comes from a time when anyone of any persuasion was a possible partner and Jack is clearly shown to be bi.

Russell T Davies, who was the show’s creator and script editor, cut his ties with the BBC and Doctor Who to move to California, and it seemed that Torchwood was finished. But the US channel Starz was interested. The first three Torchwood series were made by the BBC with co-funding by Canadian Broadcasting Corporation and located in Cardiff, Wales. The fourth series 'Torchwood: Miracle Day' was a US Starz/BBC co-production and featured CIA agents co-opting Gwen Cooper and Captain Jack to solve a mystery.

The Doctor Who of Russell T Davies and Torchwood has had a focus on death. His Doctor's bitterness was a result of being the last of his kind after his race and home planet were destroyed by war; Captain Jack was made immortal and suffered being killed multiple times only to come back into existence. In 'Miracle Day' no-one dies, human life is not extinguished by accident, illness or violence. The ramifications of that are explored. But Captain Jack finds that his wounds that previously would immediately heal now don't and he realises that while everyone else is immortal, he no longer is.

By the Autumn/Fall of 2011,(UK broadcast time), Torchwood One in London and Torchwood Three in Wales are destroyed, and contact with Torchwood Two in Scotland had been lost long ago. There was a Torchwood in India and possibly other parts of Queen Victoria's Empire.

Though Torchwood is an adult spinoff from the Doctor Who series, because of the popularity of Doctor Who many children wanted to watch Torchwood, and edited versions were produced for family-friendly viewing. Also the sixty minute episodes shown in the UK were cut by ten minutes for showing in the US. From the second series onwards adult content was limited and made easy to cut out. So it is possible that when UK viewers saw Captain Jack, in Miracle Day, cross the road to visit a gay bathhouse that scene was lost in translation.

Torchwood has been constantly changing, unafraid to explore adult questions, willing to kill of leading characters and showing characters change as a result of their experiences. Gwen Cooper had changed from a naive young copper with an in-the-dark husband to a tough as nails operative with a baby and supportive husband.

Will we see a fifth Torchwood series or has it burned itself out? The word on the web is that Starz are interested in funding another season. But has Torchwood moved too far from its original premise so that a new series would be sci-fi but not Torchwood?

Gwen Cooper is played by Eve Myles
Captain Jack Harkness is played by John Barrowman