The Oscar-winning British playwright behind Mozart biopic ‘Amadeus’ has passed away aged 90.

Sir Peter Shaffer, the playwright behind the hit plays Amadeus, which became a multi-Oscar-winning film in 1984, and Equus, has died aged 90 at the Marymount Hospice in Cork, Ireland. His niece Cressida was by his side as Shaffer “passed away peacefully,” according to a statement issued by the playwright’s agent, Rupert Lord. The statement continues, describing Shaffer as “one of the true greats of British theatre, a wonderful friend, wickedly funny man and sparkling raconteur who loved music, painting and architecture.” Shaffer only became seriously ill last week, so despite his advanced age, his death has come unexpectedly for his family and friends.

Shaffer was most notably championed by the National Theatre in London, which presented the world premieres of many of his plays. In a statement, National Theatre director Rufus Norris described Shaffer as “one of the great writers of his generation,” adding, “The plays he leaves behind are an enduring legacy.”

Among his 18 stage works, Amadeus and Equus have enjoyed the most widespread international success, with both plays earning Shaffer a slew of gongs including two Tony Awards. The 1980s film adaptation of Amadeus, which premiered in its stage format in 1979, propelled Shaffer to international attention and gave popular prominence to one of classical music’s most enduring legends regarding the alleged rivalry between Mozart and Salieri. It also earned Shaffer an Oscar for Best Screenplay at the 1985 Academy Awards and continues to be one of the most popular films about classical music ever made.

Daniel Radcliffe in the 2007 production of Equus

Written in 1973, Shaffer’s psychological thriller Equus tells the story of a disturbed teenager who has a dangerous fascination with horses. In 1977 it was also adapted for the screen in a film starring Richard Burton, Peter Firth and Jenny Agutter, but it enjoyed its most recent stint in the spotlight in 2007 when Harry Potter star Daniel Radcliffe made his West End debut in a revival of the play.

Born in Liverpool in 1926, Shaffer’s twin brother Anthony (who died in 2001) was also a widely successful author and playwright. Educated at Hall School, Hampstead and St Paul’s School in central London, before reading History at Trinity College, Cambridge, it wasn’t until the age of 28 that Peter Shaffer would discover his passion for theatre. His first play, The Salt Land (1954) was presented by the BBC, and from this debut success, he began to slowly establish a name as one of Britain’s most interesting stage writers, although he was not prolific, producing only a single work every few years. In the early 1960s, with the founding of the National Theatre, Shaffer found a regular outlet for his plays, and virtually all of his subsequent works were premiered by the NT.

Shaffer’s career ran parallel to many of the UK’s most prominent theatre luminaries, including Sir Trevor Nunn, Sir John Gielgud, and Dame Maggie Smith. Like his esteemed colleagues, his talents were also recognised by the Crown, receiving a CBE in 1987 and a knighthood in 2001.

The National Theatre will be presenting a stage revival of Amadeus later this year in October, a fact that Shaffer’s agent said was a point of particular pride for the playwright. Shaffer is survived by his brother Brian, nephews Milo and Mark, and nieces Cressida and Claudia.