The Red Shoes was on TCM on New Year's Day, it has an 80%+ audience rating on IMDB (very rare for any film pre-1970), it became the basis for Darren Aronovsky's
Black Swan. After watching it I suspected Mila Kunis and Natalie Portman didn't actually do any dancing. The physical demands of ballet are too severe for any actor to pick up on the fly. Director Michael Powell cast a professional ballerina in the lead role of his film - probably cheaper, no need for extra training. Her name was Moira Shearer.
Scottish lass from Dunfirmline, became Prima Ballerina at Covent Garden in London.