Richard Clark, who will be directing 2 episodes, has written on his twitter acccount that he was:
In the thick of Dr Who. New drafts coming along. Mark Gatiss story wonderful.From what Clark tweeted, and from the fact that Neil Gaiman himself revealed that his episode will probably be the third to air, it appears that the Mark Gatiss episode will air right after Gaiman's, making it the fourth story when the series begin in the spring:
I suspect these 2 [the Neil Gaiman and Mark Gatiss episodes]with go out 3&4 as planned - splitting series in two will leave less wriggle roomThere you have it. I hope the new Gatiss episode will be better than Victory of the Daleks, which was one of my least favourite episodes from last series. But having seen The Great Game, Sherlock's last episode which Gatiss wrote, I know he can be utterly brilliant, so I'm crossing my fingers for an awesome episode.