The public dance connects you to your audience. The connection between you and the beat is private. As long as you keep that privacy, you will be eternally unattainable, no matter what you are wearing or not wearing.
Oh, that is ... stunning, really.

I love the idea of Mary dancing for Watson, on their wedding night, and her bravery in breaking the mores of Victorian society to do so in the dance hall, to save that young woman.