The playwright Sir Peter Shaffer, whose critical and popular successes in the West End and Broadway included Equus, Amadeus, and The Royal Hunt of the Sun, has died aged 90. His agent, Rupert Lord, said: “He was simply at the end of his life but delighted to have been able to celebrate his 90th birthday with friends and then, I think, decided it was time.” The National Theatre, which staged the world premieres of many of his plays, and was already planning the first revival of Amadeus at the theatre since it opened there in 1979, described him as “an...