His voice is the most beautiful thing! <3 Lovely animation. I don't know when the accent slips but I feel the difference between this and, say, Sherlock's accents. I any case I really adore this scene. So funny!
Bless...! He never did sound English to me... the fact he never said arse, but always ass particularly grated. Quite how people were surprised he was American I never understood. Personally I fanwanked it that he had been away from England for too long!
Now Alexis Denisof had an excellent English accent! Very believable.