Taking over from Christopher Eccleston, Tennant's energetic, lightly comic portrayal quickly secured a legion of loyal fans. Understandably, the news in October 2008 that Tennant was leaving the show created palpable shockwaves among the series' followers.
Now the time to say adieu to Tennant's Doctor is nearly here.
The second of four specials that mark his departure was broadcast on November 15, with the final two parts to be shown over Christmas and the New Year period, when Tennant will 'regenerate' into the eleventh Doctor, to be played by Matt Smith.
As befitting the end of an era, the second of the specials, entitled The Waters Of Mars, which is co-written by Phil Ford and Russell T Davies, who is also leaving the show, was set to be one of the most terrifying and dramatic yet.
The teaser trailer reads: "Mars, 2059. Bowie Base One. Last recorded message: 'Don't drink the water. Don't even touch it. Not one drop'." It's an an episode which sees The Doctor and his companion Adelaide, played by the acclaimed actress Lindsay Duncan, face true terror on the Red Planet.
"It tells a different sort of story I think," says Tennant, all wide eyes and jerky gestures that lend him a slightly hyperactive air. "It's a long time before the Doctor takes control and I think that's what's unnerving about it, it's not the standard kind of structure," he adds.
"We expect the Doctor to take control earlier, we expect the Doctor to know how he's going to do it and how he's going to win through and he sort of doesn't. And even though he wins in the end, it's a bittersweet victory. And people die and that's part of the story we had to tell, to go where we're going. It's intense."
Tennant admits there's a sense that the tenth Doctor's days are numbered. "Storm clouds hang over the last series," he's said. "Things start to happen that mean things can never be quite be the same again."
As tough as it was for the 38-year-old Scot to decide to leave when he did, he says he's pleased his time as the Doctor is satisfyingly wrapped up, while hinting at a new future.
"Yeah, it feels like we need to have a big 'end of an era' story and to get on, which I think is important in this show, which let's face it has been going a long time before we showed up and no doubt will carry on into the far distant future. I think we tell a big old farewell story and then hand it over in rude health."
As is the way in TV-land, events move at a frantic pace and paparazzi pictures of the new Doctor filming on the streets of Cardiff have already been leaked to newspapers.
"I remember thinking that will probably happen, that we'll probably start seeing snaps of them [Matt Smith and his new assistant, Karen Gillan] on street corners and wearing anoraks and having cups of tea between takes. I was nervous about how I'd feel about that," he says. "Of course you feel a little bit proprietorial but I've just been really excited to see that it's going on.
"I remember what it felt like to be where Matt is now and it's really exciting to be seeing someone else starting out on that journey again."
Despite beating Tom Baker to the title of 'Best Doctor Who' by the fans of Doctor Who magazine, Tennant remains humble about attaining such an accolade. "It's been an incredible, slightly surreal experience to finally be up there and be part of that," he says. "It's something that I will be forever proud of."
Although he reveals that shooting the final scene wasn't as emotional as he'd expected. Due to the series being filmed out of sequence, Tennant's last day as the Doctor was actually spent on the set of the spin-off series, The Sarah Jane Adventures.
"The last line I said as the Doctor is half-way through an episode and it's, 'You two, with me, spit spot'. They were the last words I uttered in the suit, so I guess it was robbed of any epic quality!" says Tennant laughing. "That was probably best because it was very emotional saying cheerio and filming the very, very final scene was very sad. If the scene had coincided with the actual final day, I'd have been in trouble. I was in a bit of trouble as it was, but I was alright, I kept a mildly stiff upper lip!"
Reflecting on his time as the Doctor, he says without question the most rewarding aspect has been the star-struck reaction of the show's younger fans. "Quite often, when I meet kids, they don't know what to say," he says. "They get a bit overwhelmed by it, which I remember is what it did to me. I remember how enthused I got by the worlds that Doctor Who took me to and how special it seemed. When you feel like you're creating a similar world for a child and you see it reflected back because they don't know how to express it or how to say it, that's very special."
But is it as special as finding your face plastered on an array of merchandising items? For when it comes to a series as popular as Doctor Who, there are the requisite off-shoots, such as Doctor Who bath bombs, Doctor Who lunch-boxes, Doctor Who cuff links, you name it, the Doctor's face has probably been on it.
So what's the strangest item Tennant's seen his face on? "Pants," he says. "I think pants are probably the oddest, because they're um... pants... I'm wearing some now!" he says, presumedly joking.
"Oh, and I do have some plastic action figures. I quite like having a plastic homunculus of myself. It's a very odd thing and I'm not sure if it's entirely healthy, but it's quite fun!"
Extra time - David Tennant
It was Tennant's charismatic turn as Casanova that propelled him into the spotlight in 2005.
Asked whether he'd do an American version of Doctor Who, Tennant says, "I'll do it I can do the accent - that was a joke don't print it!"
Tennant admits owning his own Doctor Who 'sonic screw-driver' and has put it in a secure location in case his house gets burgled and he'd lose it.
Tennant recently played Hamlet to critical acclaim and a TV version of the play is imminent.
He will appear as Lord Pomfrey in St Trinian's 2: The Legend Of Fritton's Gold next month, alongside Colin Firth.