"The Black Swan" was made some months after the closing of the Festival of Britain in September 1951. It was made in response to frequent suggestions from Telekinema guests for a ballet film in 3-D, but ultimately found exhibition in commercial cinemas.
"The Black Swan" was made using a 3-D camera rig designed by Leslie P. Dudley.
As it is probably virtually impossible to find this short film anywhere, and even more so in 3D, it is worth noting that Flicker Alley included it their "3-D Rarities II" Blu-Ray film archive. Although it would certainly play on a 2D set (obviously, in 2D), it would require a set that supports 3D, in order to see it as it was intended to be shown.