Somebody asked me this the other and I want to put your minds at rest. Although it is usually the case when the Doctor regenerates that a new series starts and many of the characters or storylines are not carried through from previous series I am going to do things differently. Series 4 of Christel Doctor Who will not forget the previous going's on in Christel Doctor Who. As you already know the Contingent, who were born out of the Guardians of Time interference in the time war, will feature heavily.
There will also be reference to a number of previous characters and events. So don't worry CDW fans, its not all change.