This story arose out of a personal disaster for me. My computer suffered exactly the total breakdown that Mickey’s computer and all the others in this story suffered. And the man at my regular repair shop was perplexed because it was the sixth one he had in that day with the same problem. It was a perfectly still day, no lightning storms that are the usual cause of the sort of power spikes that cause computers to fry, no power cuts, none of the usual suspects. Well, it cost me the last credit on my credit card to replace the computer, happily with a much better one than before, but I could have done without the drain on my finances. The silver lining on the saga was that it gave me an idea for an Unfinished Business story. I thought first about the possibility of some entity interfering with the computers in the same way as the Dalek downloading the internet in the 2005 episode, Dalek. But it seemed a bit too obvious. At the same time I was considering a plot where Rose finally had to face her nightmares of The Doctor regenerating into Doctor Number Ten. And as this story slotted into the sequence the week after the first episode of the series to star David Tennant, it all fell into place. The power surges would start from the TARDIS, and be caused by a duplicate TARDIS from an alternative universe materialising inside their TARDIS. And yes, I admit I WAS very mean to Doctor Number Ten. When I wrote this I hadn’t seen anything of Dave Tennant’s portrayal of The Doctor. Christopher Eccleston’s exit from the show was still something of a raw wound, and I didn’t think I could like him as The Doctor. So he does come across rather unsympathetic in this story. And Number Nine really does not get on with him at all. Rose can’t come to terms with him at all. The only one who doesn’t bear him any illwill is Mickey, since he doesn’t know who he is exactly.

The crisis averted, though, the story reaches a conclusion satisfactory to all as The Doctor and Rose share a real, full on kiss at last as the chimes of midnight sound. They have prevaricated for so long. But the time was right, at last. Perhaps because meeting his other self made him realise he had to grab the chance while he had it. But their relationship has reached the point where not to kiss properly, not to acknowledge their relationship, would be too much.

And what DID #10 tell #9 about what happened to Rose in his dimension. Well, at the time I didn’t know, of course. But there had been rumours in the papers that Billie Piper would not do more than one more season. So a way for her to bow out had to be devised. And I guessed it had to be a traumatic one. So Doctor #9 being shocked by the answer was always going to be justified in the end. But I couldn’t give ANY detail because I hadn’t any. But anyway, it worked well enough as a mystery.