Originally Posted by trollface:
“The character was originally written to leave at the end of series 3 and then come back for a few episodes of both Doctor Who and Torchwood. This would have happened had every person in the country hand-written RTD a letter saying how much they love Martha and delivered it to his doorstep by hand. It has no connection to her popularity whatsoever.”
Exactly.
While we may not like some of the things he does sometimes and agree with him he's very true to his characters. He has pretty much stated that for Martha to just have gone 'ok' and continue travelling with the Doctor would have been a betrayal to her character. There would have been no resoluton to the arc.
Also Russell has stated that the theme for next series is the Doctors extended surragate family of friends and that is what the final Martha/Doctor scene was setting up. That it wasn't the usual 'I'm off, you're on your own again', with Martha it wasn't over, that although they were parting they still shared a relationship and a responsibilty for each other. I personally thought this was one of the most important and changing moments in the series. The Doctor has always just moved on, when something ends it ends, it has always been key to his loneliness but for the first time he wasn't allowed to do this and like I said from Russells comments about series 4 this is gonna be one of the big themes.