Writer Roland Moore, creator of the BBC TV series Land Girls, makes his Torchwood debut with this episode. He said: "The idea of this story came from my love of mazes. As a kid, I’d get my parents to take me to any place where you could get lost in a maze – and yet there was a way out. For poor Dean and Anthony, there’s no way out of this maze!

"The other things that spurred this story were my love of M. C. Escher and the episode of Seinfeld where the characters are trapped in a car park! They’re pretty nightmarish places, car parks, and if this gives people a moment of unease the next time they go into one, our job will be done."

Actor Gareth David-Lloyd added: "Ianto has always had that darker side to him – not so much that he's cruel, but he enjoys seeing people getting their comeuppance. You see a glimpse of that sadistic quality in this story."

And, producer James Goss said: "Roland’s written an adventure that’s absolutely Torchwood – down-to-earth, a little grubby and sometimes sordid. Lots of sci-fi stories have done time loops but no-one’s done one in a smelly carpark stairwell before!"

Robert Vernon, Gareth Davd Lloyd, James Glyn