This is the official definition as given in our quarterly 'The Gentlemen's Gentleman': 'A great butler must be possessed of dignity in keeping with his position.'
11 seconds sound clip from the The Remains of the Day movie soundboard.
You can hear this line at 00:17:49 in the Blu-ray version of the movie.
Quote context
[...]
- I'm sure, even you Charles, have ambitions to rise in your profession.
- I wonder if you realize what it really takes to be a great butler?
- Takes dignity. That's what it takes.
- Thank you, Mr. Stevens. Dignity, that's right. Dignity.
- Not turning a hair, he goes straight to the drawing room.
- And whispering, so as not to upset the ladies.
[...]