Take a gander at this video, which records Paul McGann’s audition for the 1996 Doctor Who TV movie. Of course he won the role, and on the basis of this performance, it’s not hard to understand why he was tapped as the Eighth Doctor.
Obviously, McGann is working with “sides,” scripts prepared specially for auditions, and some of this footage includes material that wasn’t included in the movie, such as explicitly stating the relationship between the Doctor and the Master.
It’s interesting to see this laid-back, very calm Doctor, a characterization we’ve never seen before. He seems to be almost American cool, that kind of laconic, understated Steve McQueen cool. Perhaps McGann was thinking an American audience might appreciate a McQueen-inspired interpretation. But when it came right fown to it, the characterization was abandoned in favor of something more familiar — and mercurial.