That's what Jimmy does, he pushes the boundary and then goes beyond it.
I was being rude at really inappropriate moments." Rudeness doesn't come naturally to Tennant. His father became the Moderator of the Church of Scotland - "that's our equivalent of the Archbishop of Canterbury".
But Tennant does talk about the weight of responsibility that comes with playing the Doctor.
With uncanny prescience, he told them that one day he wanted to play his hero - Doctor Who.
He has already filmed his first lines for this childhood-fantasy-come-true.
But anyway, I'm used to doing English accents." Does he object to having his Scots brogue stripped from him, as some reports have suggested? I don't feel any great nationalistic need to be Scottish. "But I don't understand why there's this thing that actors from a certain place have to speak with the accent of where they come from otherwise they're somehow being un-Scottish.
That feels very 'small nation' to me, and I think Scotland's a much bigger nation than that." Roused from his early-morning languor to a state of almost crossness, you can suddenly see why directors respond so well to this actor. Testament to this charm is the way that he won the plum role of Doctor Who after impressing its writer, Russell T Davies, when he worked with him on Casanova.
His mother looked after him and his older sister and brother as they grew up in Paisley amid the usual bustle of a minister's house.
"There were always people dropping by, but it was what I'd grown up with so I never thought, how odd, why isn't my father going to an office?
He leans back in his chair on the terrace of a Mayfair café without causing a flicker of recognition among passers-by. But I think everyone understands what it feels like to be dumped." He coyly admits to past obsessions with the opposite sex.
He wants to talk about his latest project, Secret Smile, which sees him playing Brendan Block, a "deeply misunderstood" individual, Tennant says, with typical understatement. "It's always a very intoxicating and irrational thing to be that obsessed with someone.
For someone "pure and clean", he certainly likes art and literature that examines the bleaker side of life.