When the Doctor called on allies for help in A Good Man Goes To War, it seemed strange that Captain Jack wasn’t one of them. Now, Steven Moffat has explained the reason why.

I’d have [brought back Captain Jack] for ‘A Good Man Goes To War,’ because it’d be obvious for him to call upon Jack in those circumstances,” Moffat told TVLine. “But John [Barrowman] was busy doing Miracle Day.”

However, Moffat doesn’t rule out a return in future: “When we’ve got a good story, we’ll do it,” he says.

“You can’t just bring somebody back and say, ‘That’s a story.’ That’s just somebody walking through a door…. I won’t be thinking, ‘How do you bring Captain Jack back?’ I’ll be thinking, ‘You know what this needs? We need to bring Jack back for it.’”

But while Moffat is fine with Jack coming back to Doctor Who one day, he thinks we’ll never see our favourite Time Lord turning up in Torchwood: “The Doctor could never go to Torchwood,” Moffat attests. “Russell [T Davies] and I both agree on that. Doctor Who has a tremendous relationship with children in Britain. They’d want to watch Torchwood then, and it’s not really a children’s show.”

Barrowman recently said he’d love for Jack to return for Doctor Who’s 50th anniversary in 2013.