Is the middle atlantic style.
The blending of American Ivy and European tailoring.
A darted 3/2 roll sack suit with pleated trousers.
Cary Grant was the master in this field.
Indeed, and that accent, what was it? Not the BBC Radio 1 cod phony mid-Atlantic accent, but something else entirely: not American not English, somewhat world weary and effervescent at the same time. Of course, that was all part of the enigma that was Cary Grant.
Something other than his regular English accent for this film?
He emigratred at 16 from Bristol and spent his late teens to twenties touring round as an actor so he probably played on a Bristol twang and encorporated bits he liked