Francis Duncan is the pseudonym for William Underhill, who was born in 1918. He lived virtually all his life in Bristol and was a 'scholarship boy' boarder at Queen Elizabeth's Hospital school. Due to family circumstances he was unable to go to university and started work in the Housing Department of Bristol City Council. Writing was always important to him and very early on he published articles in newspapers and magazines. His first detective story was published in 1936.

In 1938 he married Sylvia Henly. Although a conscientious objector, he served in the Royal Army Medical Corps in World War II, landing in France shortly after D-Day. After the war he trained as a teacher and spent the rest of his life in education, first as a primary school teacher and then as a lecturer in a college of further education. In the 1950s he studied for an external economics degree from London University. No mean feat with a family to support; his daughter, Kathryn, was born in 1943 and his son, Derek, in 1949.

Throughout much of this time he continued to write detective fiction from 'sheer inner necessity', but also to supplement a modest income. He enjoyed foreign travel, particularly to France, and took up golf on retirement. He died of a heart attack shortly after celebrating his fiftieth wedding anniversary in 1988.