York was born in Fulmer, Gerrards Cross, Buckinghamshire, the son of Florence Edith May (née Chown), a musician; and Joseph Gwynne Johnson, a Llandovery-born Welsh ex-Royal Artillery British Army officer and executive with Marks & Spencer department stores. York has an older sister, Penelope Anne (born 1940) and younger twin sisters, Caroline and Bridget (born 1947); Bridget died a few hours after birth, according to his autobiography. He was brought up in Burgess Hill, Sussex.