There's an interview with David Tennant in next weeks issue of the TV Times (out today). The TVTimes website says "And talking of monsters, we've also got a special preview of Doctor Who's upcoming third season, as star David Tennant guides us through the weird and wacky people and places the Time Lord and his new assistant Martha Jones will be visiting in the new run."
I've seen a scan of the first page of the interview and the first paragraph includes the phrase "he's denied reports he's quit the show". However the final part of the interview actually only goes as far as to quote him as saying "You shouldn't believe everything you read in the papers".
I like the title of the article - Who's a Busy Boy!
