English ballet erupted out of the second world war in the hands of the rival choreographers Frederick Ashton and Robert Helpmann, colleagues but of different instincts, one for dance, the other for drama. The case is currently being made for each by the Royal Ballet and Birmingham Royal Ballet.

But how to revive the sensations and imaginings of the 1940s? It was long before most of us were even born, and more than any other art form ballet is dependent on evoking memory, atmospheres, intangible associations.