You imply rather that you didn't know she was female at first ("as it turned out").
Sorry, Mary, should have answered this earlier: there were two performers listed for Miles, one a local lad, and the other this Belgian girl: according to the schedule, it was to have been the boy, and since there was a girl the spitting image of the photograph in the programme sitting around the circle from me, I assumed that it was the alternative who was watching. It was a very knowing performance for a child, though this was an older-looking Miles than we're used to; into his teens rather than the little angel; if I remember correctly the other Miles was that same age in real life, and a head chorister somewhere, according to his biog. I mentioned before the extraordinary moment at the end of the Bell scene after his last words ("Does my uncle think what you think?") when before his exit, he stared the Governess straight in the face, kissed the tip of his index finger and laid it gently on her forehead before running it lightly down her nose until it rested on her lips as an admonition of silence before he moved away offstage to join the others. The Governess's next lines ("It was a challenge!/He knows what I know, and dares me to act...") seemed more pertinent than ever.
In the clip you can also see one of the screens which had projected images and clips on: in this case the eyes of Quint are watching. It's also possible to see from the costumes that the action has been moved to somewhere in the first half of the twentieth century, perhaps around the late thirties/early forties, but this is one of those cases where it makes as much sense as the Victorian or Edwardian period more normally associated with the work.