Although you're never going to read this, I thought it necessary to get my thoughts off my chest in response to the comment you made in December 2013 to SFX magazine. The comment I'm referring to is where you say, "I’m confident that we’ll sell this Doctor to our existing audience and he will be different enough that people won’t just be miserable that they’re missing Matt.” The media picked up the story with quoting you as saying, "Capaldi will win over Smith Diehards."
First of all, I am not a Smith Diehard fan. I have watched all of the episodes in which Matt Smith has starred as the Doctor, but he is not my doctor. You could probably hazard a guess at which Doctor is my Doctor, but I shall give you some history about my time as a Doctor Who fan first.
Although I don't remember any specific scenes, my first Doctor was Sylvester McCoy. This is the first Doctor I remember watching. From those two facts alone, I imagine that you could peg me as a fan who started watching in the late 1980s. My age? Less so, but let's just say if you said you assumed I was either in my late 20s or early 30s as of this date, you would be right. You don't turn around to a child of any age and say, "This is your doctor. This is the doctor you're going to idolise and remember as your doctor." I can assure you that parents of Doctor Who fans don't enforce who their children have as their doctor! My father's favourite doctor still is Peter Davison, who unfortunately probably has never reached my top three favourite.
As you probably don't need telling, many Doctor Who fans between the ages of let's say, 25 and 40, didn't have the show available to them for over 15 years of their childhood save the Paul McGann episode aired in 1996. Now I know that there are fans of Mr. McGann as the Doctor despite until recently his one appearance (I will applaud you for bringing Mr. McGann back to the role of the Doctor after 17 years even for 7 minutes) and due to the endless work by those writers who have dreamed up adventures for his incarnation. Despite the shortest televised tenure in the history of the show so far, the eighth Doctor still has his loyal fans, and rightly so. You captured even in a few short minutes why Mr. McGann had been sought out for the role over 17 years ago, and how he could have been such a memorable Doctor. Such a shame that he hasn't yet fought his famous foes. You know the applause that the entire fanhood gave you for bring Mr. McGann back recently, and that this came from not only fans who had Mr. McGann as their doctor, but fans who were utterly amazed that it was Mr. McGann in the mini-episode "The Time of the Doctor", and not Mr. Smith, David Tennant or Mr. Hurt, whom we knew all would be starring in The Day of the Doctor. If scheduling permits, please give Mr. McGann his own series as the Doctor, even if it's just for 13 episodes. 
However, all was not lost for a child in the U.K. in the 1990s. BBC 2 aired a number of stories from the 60s, 70s, and 80s, and for any fan of the show, this was a treat! I discovered the Doctors I hadn't been introduced to before, and I won't deny that Mr. McCoy slid out of being my favourite Doctor. His successor? Jon Pertwee. At the time I didn't even put recognition that this was the same actor who portrayed Worzel Gummidge, and it didn't even matter: I never knew whether to like or loathe the scarecrow, but I thought the Doctor travelling around in Bessie was wonderful. Remember I said that Mr. McCoy was my first Doctor? By the mid-1990s, Mr. Pertwee was my favourite Doctor. And there was no one telling me who my allegiances should go towards. I made that decision on my own.
You of course will have much more distinct memories of Doctor Who returning to the screens in 2005; I imagine that you were privvy to many pieces of information that never filterated onto the Internet. You should be applauded for your two-parter, The Empty Child and The Doctor Dances, for introducing a memorable character such as Captain Jack Harkness.
For generations of children and adults, Christopher Eccleston was their first Doctor. At no time do I recall anybody insisting that Mr. Eccleston was the Doctor for everybody. It's possible that there are fans for whom Mr. Eccleston is their doctor, regardless of whether or not they felt any affection for the previous eight actors. I shall readily admit that I thoroughly enjoyed the ninth incarnation of the Doctor, although I don't think I ever said, "This is my Doctor".
Despite Mr. Eccleston's desire to only reintroduce the Doctor for 13 episodes, we were lucky enough that the producers managed to sought out Mr. Tennant for the role of the Tenth Doctor. I don't know that I wanted to admit here, or to keep you guessing, but David Tennant is my Doctor. He's been my Doctor since I got to the 39th minute of The Christmas Invasion, once he's been rejuvenated by a cup of tea, and he proceeds to fight the Sycorax. If Russell T. Davies ever proclaimed, "If you liked Christopher Eccleston, you're going to love David Tennant," I never read the quote. No one enforced me to like the Tenth Doctor, to take him as my favourite, to proclaim that he was My Doctor, but that's what I did. 
For four years, I laughed, I giggled, I cried; I felt emotions watching Mr. Tennant that he portrayed on screen. He was my Doctor, and I loved watching each and every episode he appeared in. And when, heartbreakingly, I watched The End of Time (Part 2) on January 2, 2010, and the Tenth Doctor uttered his final words, "I don't want to go," I sobbed back at my television screen, "I don't want you to go either." (And yes, my heart broke when the same words were spoken in The Day of the Doctor.) 
This brings you to the more recent tenure of Matt Smith. As I mentioned earlier, I've seen every episode Mr. Smith has portrayed the Doctor in. He's been witty, hilarious, and moody when the time calls, and he has had different relationships with his companions than his predecessor. I can understand why fans are calling the Eleventh Doctor (I'm sorry, I can't go referring to them as their latter incarnations) their Doctor, but he's not mine. You've never told the audience that "Matt is your Doctor" and not even one of my friends who has changed allegiance from being a Tenth Doctor fan to the Eleventh Doctor fan (and a big one at that!) has tried to make the Eleventh Doctor my doctor. (On a side note, if we ever watch The Day of the Doctor together, we have to have individual doctors to fawn over!) I can understand the appeal of the Eleventh Doctor, but the Tenth Doctor is my doctor. Which is why I'm perplexed that you're proclaiming that Mr. Capaldi will win over Mr. Smith's diehard fans. I'm not saying Mr. Capaldi won't make a great Doctor; I'm sure that you wouldn't have casted him in the role if he wasn't going to bring something special to the role. However, you need to allow the fans to make up their own minds. I'm not saying that I'm a forever diehard David Tennant fan, but I shall be surprised if and when I change my allegiance to Peter Capaldi. Needless to say though, that should be my decision, and it shouldn't necessary happen during the Christmas special, even if the rumours are true and Mr. Capaldi appears on screen midway through the episode. How do you know that you've given the Doctor enough time to save the day and to showcase the character he might be? Surely this is why you're ensuring that Mr. Capaldi's first full series is 13 consecutive episodes rather than a split season?
Mr. Moffatt, you have brought some truely amazing storylines to screen over the last eight years. You've given us wonderful characters in the shape of River Song, Amy, Rory, Jenny, Strax, to name a few. But please don't tell the fans how they should feel.
I realise the show is about change. Like any change, people adapt and accept changes differently. Accepting a new actor in the lead role is no different: there will be fans who will accept Mr. Capaldi immediately, and to whom he will be their doctor. There will also be fans who will stay devoted to their current favourite doctor. It's natural. I hope you understand that, and I hope that you don't continously force Mr. Capaldi onto the public to accept him. You've casted him, you knew he will do a great job. Just give him a little while longer to start amassing his fanbase, will you?
