Although I had undoubtedly come to Snape that evening solely in order to hear Ian Bostridge sing Britten and Tippett, I left feeling the most astonished, and exhilarated, by Britten’s extraordinary String Quartet no. 1, played with blistering skill and forensic intensity by the Arcadia Quartet. Britten’s String Quartet no. 1 had a tremulous, magical opening into which…