Underground was sparked simply by an idea of having Jack and one of the team trapped in some potentially fatal way. It didn’t take much thinking to decide that it would be Alun he was trapped with. He is the one who has the least history with Jack, professionally and emotionally, and the fact that Ianto loves both of them would make the anxiety above ground even more pronounced.

It was not intended to be an action story, of course, but was just about the two of them, Jack and Alun, talking to each other, trying to boost each other’s spirits, and just stay alive. I put them in a position that would, in any other situation, be called compromising, and had Jack with a broken back that, for anyone but him, would have been a terrible injury with far reaching consequences, and let them talk about every subject from what happens if they need to pee to whether Alun ought to say yes to Ianto’s proposal to him.

The structure of the story went through a bit of a last minute rewrite. Originally I didn’t intend to have any intercut with the search for them in any way. The story would be entirely from Jack and Ianto’s point of view, at least until the last when it switches to Ianto and Owen waiting anxiously. It worked all right, but there was a danger that it would feel just like one long conversation between the two. A lot of fan fiction seems to be Jack and Ianto in the office talking around to a snog. I wanted to get away from that. Breaking up the underground parts with what was happening overground helped. Also it meant that it was less abrupt switching from the underground to overground at the end. I didn’t want the rescue to be from Alun’s point of view. For one thing, he was unconscious, and for another, I am not familiar enough with the methods used by the professionals in situations like that to actually tell the story properly. Better to leave them to it and have them bring the bodies out on stretchers.

I decided against it being a deliberate kidnapping and burial underground, mainly because it has been done so often – it is a tried and trusted plotline. It’s been done in several TV shows. The most famous of recent years was the so-called ‘Tarantino’ episode of CSI Las Vegas, which had a central character buried alive and running out of air. An episode of a slightly newer American forensic science thriller, Bones, had two of its main stars in a buried van with the air running out and finding some ingenious ways of keeping themselves alive. But a good story can always be retold. And South Wales is full of old coal mines, thanks to Conservative policies that shut most of them down. The Uzigi were a good reason for them to be there in the first place. I briefly tinkered with the idea of it being the mine in a small village near Cardiff called Llanfairfach. It would have been an interesting twist, but I decided the story didn’t need it.

I started without the problem of air, giving them a flow coming from somewhere. Only later in the story, after a further rock fall blocked that off, did it become a new peril. It gives the story a new impetus just at the point where the two of them talking to each other could start to drag. Then, of course, Jack gives Alun the last resort. Jack has to DIE to buy Alun a bit more chance of rescue. That’s the element that CSI and Bones don’t have - a man who can die and come back to life. One of these days it COULD be the one he doesn’t come back from. But probably not while I’m writing them.