Denise Holt was born on 1 October 1949, the daughter of William Dennis and Mary Joanna Mills; she was educated at New Hall School, Chelmsford [Essex] and the University of Bristol. In 1987 she married David Holt, having one son.

She joined the Foreign and Commonwealth Office in 1970 and her diplomatic career included: Research Analyst, initially on the Iberian desk, 1970–84; First Secretary, Dublin [Ireland], 1984–87; Head of Section, FCO, 1988–90; First Secretary, Brasilia [Brazil], 1991–93; Deputy Head, Eastern Department, FCO, 1993–94; Assistant Director, Personnel, 1996–98; Deputy Head of Mission, Dublin, 1998–99; Director of Personnel, FCO, 1999–2002; Ambassador to Mexico, 2002–05; Director for Migration and Overseas Territories, FCO, 2005–07; Ambassador to Spain, 2007–09.