I agreed to drop Scots accent for Doctor Who - Tennant
The 34-year-old actor said scriptwriter Russell T Davies did not want the latest Doctor to have an accent.
The most recent incumbent, Christopher Eccleston, used his Manchester accent in the role, but Tennant stunned fans by dumping his native Scots lilt.
He said: "Russell said we'd like to not go for another obvious regional accent, because I suppose they'd done that. Not that, I hasten to add, a slightly off-London accent isn't a regional accent, because it is, but it reads slightly more generically than a Scottish accent does.
"Russell said, 'that's how we'd like to take it', and I was quite happy to go with that."
Sylvester McCoy played the Doctor from 1987 with what he has described as a gentle lilt compared to his normal Scottish accent.
Tennant hinted in his interview with SFX magazine that playing Doctor Who was not quite what he thought it would be.
He said he had been a Doctor Who "junkie" since his childhood. As a teenager, he wrote an essay about his addiction to the show and queued to meet former time-traveller Tom Baker.
It was watching the sci-fi show in its early days that made the young Tennant - whose bedroom was filled with Doctor Who posters - decide to become an actor.
But asked whether the reality of playing the TV icon matched the picture Tennant had imagined, he said: "What I realised when I came to do this was that any sort of fantastic notions one might have had about this were just that - fantastic notions.
"When you have to come and make real decisions about it, it's a different thing.
"Actors often say that the best bit about getting a job is a phone call that says you've got it, because at that moment it is all potential, and it could be anything.
"It's all possibilities, and as soon as you start making decisions, it starts becoming reality, which is never as much fun."
Tennant promised that the Doctor's relationship with Rose, played by Billie Piper, would hot up in the second series. "I think it's explored quite deeply," he said.