This is actually called a prequel by BBC definitions but what ever the case it is a good one. BBC Has always found a way to keep you hooked into the series even after what seems like forever for the next seasons arrival. The first episode of season 6 will air both in the UK and the US on April 23. That is Easter weekend for those lost in time themselves.
The prequel has former late President Nixon receiving a mysterious phone call from a girl begging him to turn around. There is a monster behind him. Kind of gives you a hint that it's the early 70's and the US that the season opener plot will be in.
So with out any more of my dribble here is the video from BBC One. P.S. the first episode is called "The Impossible Astronaut"