He is the son of Colonel Cyril Darby Military Cross, of Kemerton Court, Gloucestershire and Monica Dunne, daughter of Marten Dunne, Member of Parliament of Gatley Park, Herefordshire. He is married to acupuncturist Lady Meriel Darby, daughter of the former Prime Minister Alec Douglas-Home, and has one son, Matthew, and one daughter, Catherine.
Darby was a fellow and tutor in economics at Keble College, Oxford University (1963–1985), and visiting lecturer in environmental economics at the University of Pennsylvania in 1978. He subsequently served as chairman of Europe’s largest nature conservation organization the RSPB (1986–1993), and became vice-president from 1996 onwards. He founded the Kemerton Conservation Trust in 1989.
Darby was chairman of Plantlife International 1994-2002, and president from 2005 onwards.
He was chairman of Planta Europa 1998-2004. In 1995 he became a trustee of the Herpetological Conservation Trust.
He served as chairman of the United Kingdom Committee of the World Conservation Union (1996–1999). From 1997 he sat on the board of the Farming and Rural Conservation Agency.
He served as chairman of the Joint Nature Conservation Committee of the United Kingdom from 2004-2007.
Darby was appointed Officer of the Most Excellent Order of the British Empire for services to nature conservation in 1996. Since 1998 he has been a Liberal Democrat councillor for Wychavon District Council in Worcestershire.
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.
