I had often wondered why The Duchess of Malfi has survived as a classic, let alone a set text. Someone said it was a nightmare not a tragedy and I was never much interested in a nightmare whose plot turns on a widow’s disobedience to a pair of barmy brothers obsessed with maintaining a royal bloodline.

But an extraordinary production - plus the background pack for schools - set me straight. The notes say that the tragedy is that of a woman not allowed to define herself. The Duchess’s victory is a refusal to let others, who all have their hideous opinions, remould her and she dies declaring “I am Duchess of Malfi still”. Schools’ documentation - plus a poster of a modish Duchess wearing sunglasses and asking “will this woman dare to follow her heart in the face of public image and royal duty . . .” - interpret the self-assertion as an echo of Princess Diana’s insistence she should retain her title and be understood as a woman.

A clunking discussion line connecting the play to modern audiences is dramatised by turning the chorus into rat-pack paparazzi. Seventeenth-century courtiers’ gossip is recast as tabloid copy about glamour and perversion. Journalists humiliate themselves and the Duchess, but they don’t kill her. That’s done by Justin Shelvin’s languidly venomous Bosola at the behest of mad Ferdinand. Her death scene is one of the most sinister cabaret acts imaginable. A lunatic embracing her from the rear, the Duchess’ jaw is worked in rough mime to a male falsetto rendering of “Somewhere Over the Rainbow”. It’s a tour de force that enlightens one of the most sinister texts in the English language.

Director Kate Brooke identifies the main discussion line as the difference between appearance and reality, or definition and redefinition. It’s an inverted world where people “seem to sweat in ice, freeze in fire” and where “all honesty is laughed out of fashion”. There is little laughter, no honesty outside the love between the Duchess and her secret husband Antonio, and a lot of fashion. The setting is slick 1950s Italy and the action takes place on a catwalk carpeted in 10,000 lire notes.

It was somehow surprising that only six actors made a final bow. Aside from playing lead roles they’d been barbershop singers, journalists, radio announcers, lunatics and shrinks. The tragedy avoided the dip into unintended farce when characters die, then hoist themselves on to an elbow, make a final final speech and die again. Nobody laughed at the sad bits.

Under its new producer Fiona Clark, the Theatre Royal’s Ustinov Studio bills itself as “a major educational resource for the south west”. The standard issue outreach patter is given substance in several ways - for instance, after its theatre run, Malfi will play in schools. The theatre is also reviving a drama teachers’ association.

There are formal partnerships with several schools and colleges and many workshops covering both individual performances and general theatre skills. And, of course, the best educational outreach of all is taking a dense text such as Malfi and showing why it is still important.

Touring schools in the south west until April 4 (01225 448844)