David Tennant isn't leaving because of back problems - he's leaving because he doesn't want it to get boring. -
http://news.bbc.co.uk/2/hi/entertainment/7698539.stm"Three years was "about the right time" to play the role, he told the BBC in an exclusive interview.
"I think it's better to go when there's a chance that people might miss you, rather than to hang around and outstay your welcome," he said."
"'That's one of the reasons I think it's right to take a deep breath and bow out when it's still fun, when it's a novelty.
"I don't ever want it to feel like a job, so I want to move on when it still feels exciting and fresh and that means I'll miss it.'"
Also - new guy has black hair and looks like a vampire -
http://www.bbc.co.uk/doctorwho/s4/news/ ... 06_news_01