Gervase de Peyer was born in London and attended Bedales School. He was awarded a scholarship to the Royal College of Music where he studied clarinet with Frederick Thurston and piano with Arthur Alexander. Towards the end of World War II, when he was aged 18, he joined the Royal Marines Band Service. De Peyer returned to the Royal College of Music after the war and subsequently studied in Paris with Louis Cahuzac. 　　In 1950 he was a founding member of the Melos Ensemble for which he continued to play until 1974. He conducted their recordings with EMI.Their recordings of chamber music for both woodwinds and strings were reissued in 2011, including the works for larger ensembles which were the reason to found the ensemble, such as Beethoven's Septet and Octet, Schubert's Octet and Ravel's Introduction and Allegro, played with Osian Ellis (harp), Richard Adeney (flute), Emanuel Hurwitz and Ivor McMahon (violin), Cecil Aronowitz (viola) and Terence Weil (cello). 　　From 1956 to 1973 he was principal clarinet of the London Symphony Orchestra. He was a founding member of The Chamber Music Society of Lincoln Center in New York in 1969 and played with them for 20 years. He has conducted the English Chamber Orchestra, the London Symphony Orchestra, the Melos Sinfonia, he has directed the London Symphony Orchestra Wind Ensemble and is the associate conductor of the Haydn Orchestra. In 1959 he began teaching at the Royal Academy of Music. 　　De Peyer has played first performances of concertos by Arnold Cooke, Sebastian Forbes, Alun Hoddinott, Joseph Horovitz, Thea Musgrave, Elizabeth Maconchy, William Mathias and Edwin Roxburgh.He premiered Miklós Rózsa's Sonata for Clarinet Solo in 1987.