Anyone would have sworn that the butler was a real butler, the footman a real footman only, as it happened, the butler was Whittington! 
Whittington was doing a very good job pretending to be a footman.
mnli hypothesis: Whittington was doing a very good job pretending to be a footman. premise: Anyone would have sworn that the butler was a real butler, the footman a real footman only, as it happened, the butler was Whittington! 