Sir Topham Hatt (also known as The Fat Controller), whose attire of a top hat, tuxedo
Tuxedo! Tuxedo!! No gentleman wears a tuxedo during the daytime (unless he's coming home from an evening out).
Wiki (In his iconic top hat and morning suit,) gets it closer, but not quite right.
What the Fat Contoller correctly wears (cutaway coat and non-matching trousers) is morning dress, the wear for daytime business activities. A morning suit would have matching trousers and be worn for daytime social functions.
That said, Sir Topham's yellow waistcoat marks him out as a bit of a bohemian, and implies some depth to the character.
Tuxedo is her words not mine...