No sooner has the multi-talented John Barrowman finished judging Josephs in BBC1's Any Dream Will Do, than he's back on Saturday nights starring in the this year's climactic finale to Doctor Who. And, if that wasn't enough, a new series of Torchwood is currently in production, and a new range of Torchwood audiobooks are out now. Somehow, he found time to tell us about it all.

What's the latest on the second series of Torchwood?

Well, I've just been sent the breakdown for the first few episodes and there's a couple of surprises. I know the storylines for most of the series now, and certain things are going to change. It will be coloured very differently and will bring a lot of the humour back to Captain Jack.

Is that a result of Jack's experiences in the new series of Doctor Who?

Jack does get to resolve a lot of his issues in these three episodes. You find out a huge amount about him, including a huge secret that you could never ever possibly imagine. When you discover what it is, your jaw will actually hit the floor! I jumped around the room when I read the script. Then I ran into David's trailer screaming, "Oh my God!" He'd been teasing me for days because he'd already seen it, and he just said, "It's really cool, isn't it?"

Has working with David Tennant been very different from working with Christopher Eccleston?

David's a lot happier! I enjoyed working with Chris, and he was the man who put Doctor Who back on the map, but David's happier in himself. I go out to eat with David, and I see him quite often, whereas Chris was very quiet, and I didn't see very much of him off set. I think he's in a happier place now he's playing the invisible man! A nice guy, but very quiet and very different from David.

You got to kiss him, though. Do you get to kiss David in the new series?

Well, if I told you that I would be breaking protocol wouldn't I? Russell would probably slap my wrist – or my ass! But, really, you just don't know how the Doctor and Jack are going to react to each other. Does the Doctor feel guilty for what he's done? Jack's part of Torchwood now, which is not good with the Doctor, and the conversation has to be had that since he met the Doctor he now cannot die. There are all these issues to resolve.

Was it hard to reassess your take on Jack once you'd read this big secret?

I like to think I know Jack very well, but, when a curve is thrown, it's nice to work it out. We discussed it for ages when Owen shot Jack at the end of the last series. We couldn't get our heads around why that would happen. So we discussed it as a team and learned about the characters even more. I wanted to hear what everyone had to say, because I was the one getting shot!

You're probably one of the most shot characters on TV.

Well, now he knows he can't die, Jack's going to do everything possible to make other people live, whatever that takes. It's painful, but he knows he can come back. Maybe he does it because he's lived so long and wants to die, because all his friends have gone.

You make him sound like a Time Lord…

Ha! If he was, do you think I'd tell you? But he's not! He's a time agent!

Did you enjoy recording the new Torchwood audiobook, Another Life?

It was really good. I liked that I got to read it, rather than someone who knows nothing about Jack or the other characters. I changed some of the lines, because I knew they were things that Jack wouldn't say, and we do that when we're filming, too.

Was it hard being in a recording studio and not bursting into song?

Well, I did burst into song a few times, but it's a different kind of recording studio! I also cracked a few jokes and made a few noises from both ends of the human spectra. It's probably all on the recording somewhere.

I'd love to do a full cast recording for Torchwood, one day, with music and effects. It would take a lot of time, but it would be excellent. It's very isolating sitting in a little room with no windows and reading out loud!

I was disappointed that you didn't try any Welsh accents.

If I try to speak Welsh, I start to sound like I'm from India. That's not me trying to make fun of either, it just happens that way. I try to make the voices different in the sense that the girls are softer sounding than the boys, and Jack is Jack, but apart from that I just read it as a narrative. There was a Scottish character in Another Life, which I could have done, because I was born in Scotland, but we decided it would be confusing for the listener if I did just one accent.

How old were you when you lost your Scottish accent?

I didn't lose it. [Adopts broad Glaswegian accent] I just choose not to speak with it when I'm talking to people who don't know I'm Scottish. But when I go home with my mum and my dad and my brothers and sisters, this is the way I speak. So when I'm in America, funnily enough, I'll speak this way, and when I'm in the UK… [returns to American accent] I'll speak like this.

It must really confuse people when you and David Tennant get together.

I cannot talk to David in a Scottish accent, because he knows me as 'Captain Jack' John, where I speak to him as an American and he's English. If I start to do the Scottish accent when we're off camera, we both say, "This is weird."

Will there come a time when you say goodbye to Captain Jack?

I have always said that I would be perfectly happy to play Captain Jack for the next 10 years, as long as I could do some other things with it. I love playing him, and I love science fiction. I grew up with Star Wars and Battlestar Galactica, and I loved the Cylons just like I loved the Daleks and the Cybermen.

Do you watch the 'reimagined' Battlestar Galactica?

I couldn't get into it when it started, because the first one was so laborious. But my sister watches it and says it's really good, so I may have to give it a second chance.

You've recently had a racehorse named after your character. Is there anything else you'd like named after you or Jack?

I think I'd like an airplane named after Jack. Not so much after John Barrowman, because that would be a bit egotistical, but I think the public love Jack so much. The Flying Harkness would be fun, or a Virgin Atlantic plane, maybe.

This summer, in fact, I'm going to be a representative for the RAF and the American Air Force at the Royal Air Tattoo. The RAF is the only branch of the military that openly recruits gay men. I'm being flown in on a jet fighter and I get to make a big speech and play action man for the day with a load of guys in uniform. Sounds awful, doesn't it! That's all thanks to Captain Jack.

Doctor Who is on BBC1 on Saturday nights. Another Life is one of three Torchwood audiobooks currently available from the BBC. To win a set of audiobooks, click here.