The official Doctor Who site has interviewed Neil Gaiman, pending the release of his second Doctor Who episode tonight. The interview is split up into parts, presumably due to spoilers, and you can read the first part below.

Question: You’re back! Hurray! How were you persuaded to return?

Neil Gaiman: It began with an email from Steven Moffat. He said, ‘I know you’re too busy ever to write another Doctor Who episode… but would you like to make the Cybermen scary again?’ And I thought, Agghhhh! I do! I really do! I said,Yes, I’m in…
I thought it would be really fun to make the Cybermen scarier than they have been recently and then I got completely side-tracked by a mad, strange romp that just keeps getting bigger and odder in which the Doctor and Clara have taken two children to a big amusement park and they find themselves embroiled in a very peculiar galactic empire which has fought a battle against the Cybermen - and won…
 
Q: What can we expect from the Cybermen and the adventure in general?

NG: We’ve moved on a little bit, technologically, from the last round of Cybermen we saw, because we’re a bit further into the future. So instead of Cybermats, we’re now going to encounter Cybermites… We have to deal with various things we’ve had to deal with in the past, such as the Cybermen’s ability to take over people and transform them into Cybermen. And this time, it’s going to get very, very personal for the Doctor…

Q: It’s got a great cast! Could you tell us about them and the characters they play?

NG: I’ve been very lucky! Jason Watkins plays Mr Webley… He has a few waxworks and other things and made the rather foolish mistake of landing on Hedgewick’s World… and now he can’t get off. He’s really sweet and he is aided by Porridge who is played by Warwick Davis. And he’s wonderful! His performance is just brilliant. It’s funny. It’s charming, it’s deep… it’s very sexy! I’m very proud to have written his stuff.
We also have Tamzin Outhwaite. Tamzin is great! She plays a character who’s running a platoon – a captain. She’s grumpy and you rapidly discover that one of the reasons she’s grumpy is because this is a punishment platoon – they are in exile. These are people who’ve been in trouble and they’re being got out of the way… And she was sent there because she was not obeying orders, and now she’s going to have to make a big decision on whether or not she obeys an order…

Q: So, you’ve got the task of making the Cybermen scarier and this eclectic group of people… How did your story develop from this ‘original plot’.

NG: The only problem with my original plot was that I had no idea what I was doing with the Doctor. I knew what I was doing for everyone else in the story but I really didn’t have anything for the Doctor to do, except he was going to play chess, which isn’t really interesting. And then I had an idea. And the idea wouldn’t go away. So I emailed Steven Moffat and said, ‘Look, I have a mad idea. And it’s something that I wouldn’t do for any other actor except Matt Smith. I think Matt could pull it off. [Neil laughs and briefly outlines the Doctor’s plot-line]. And Steven Moffat said, ‘Go for it!’