Playing real people, albeit in a fictional situation, on stage can be a daunting task. Perhaps even more than on film and especially when the people are themselves actors, dancers or singers whose actual performances have been seen by audience members. Tony Award-winning Master Class by Terence McNally is about Maria Callas after the end of her stage career when she undertook to coach young singers at New York’s Julliard School.

Stephanie Beacham looks right as Callas from her first entrance, a diva (in the proper sense) demanding accuracy, intelligence and commitment to the work in hand from all around her. Her students are three – two sopranos and a tenor – and she both bullies and coaxes them to understand not just the notes they are singing but the power of the words and the emotions which these express. Class’ own biography is sketched in just sufficiently to add context.

That biography included marriage to the older Meneghini – for whom she was a treasure but whose love she could not return, and her liaison with Onassis – who saw her as simply yet another trophy to be snatched, savoured for a time and then discarded. When Beacham/Callas says that what she hears is “We love you, Never, I love you” we have the essence of the singer and the roles with which she’ll always be associated.

Director Joanthan Church paces it superbly and he allows the self-effacing répétiteur Manny (David Harvey) and the over-ambitious tenor Tony (Christopher Jacobsen) their moments of reflected stardom. Pamela Hay as Sharon, learning that Lady Macbeth’s letter-scene is more than just a matter of showing off a vocal range, and Robyn North as Sophie, being brought to realise that Amina in La sonnambula is not simply a piece of bel canto decoration, both sing and act appropriately.

And then, of course, there’s the recorded voice of Callas herself.