 Darby has served as a regional committee member of the National Trust; a fellow (governor) of Eton College (1979–1994); a county committee member of the Country Landowners Association.Since 1998 he has been a Liberal Democrat councillor for Wychavon District Council in Worcestershire.Darby is the son of Col. Cyril Darby MC of Kemerton Court and Monica Dunne, daughter of Marten Dunne, MP of Gatley Park.