I was so busy being incredulous at the crass “whoops, exposition!” opening of the late Peter Shaffer’s play, back on the stage where it premièred in 1979, that for several minutes I didn’t realise that Shaffer hadn’t written this sequence in the language of theatre, but of opera. Director Michael Longhurst takes his cue (as who could not?) from the necessarily integral role of music in Shaffer’s version of the rivalry between Mozart and his contemporary, court composer Salieri.

Longhurst stages the piece as an orchestral/operatic rehearsal. The stage is dark and bare but for occasional items of furniture or architecture wheeled on as required (leading to the occasional Terry Gilliam cartoon moment as, for instance, a couple of two-dimensional clouds fly overhead whilst a soprano is trucked about, draped around a couple of Doric columns); a raised podium moves forward and back as the Austrian imperial court and other locations; the Olivier’s revolve occasionally sinks to form a pit for the 20-piece Southbank Sinfonia. The musicians are a constant presence, even casually greeted on occasion by Adam Gillen’s Mozart.

Gillen’s peroxide-blonde mop of hair suggests that Shaffer’s vulgar, exuberant Mozart was influenced to some extent by the punks at the time of his writing. However, Gillen’s Mozart goes far further: his is not simply a case of extreme indecorousness, but outright behavioural disorder. The duality of Mozart, which so fascinated and appalled Salieri – that such divine music could issue from such a profane young man – is here taken to the degree of idiot-savant.

Lucian Msamati is blessed with a love of and flair with language that makes him a compelling Salieri. Even his slight African accent is turned to use, emphasising Salieri’s outsiderdom as an Italian at the German-speaking imperial court. For this is Salieri’s play from beginning to end, his narration of how he set out to destroy Mozart both professionally and physically. It can drag at times (and Gillen is really very good at making Mozart thoroughly annoying), but when the acting, Longhurst’s direction and Simon Slater and the Sinfonia all merge in the final Requiem sequence, the drama becomes as towering as the music.

Written for the Financial Times.