Wilcox was born in 1931 in Welwyn Garden City, Hertfordshire, England, to John William Wilcox and Alice M. Whittle. He attended Cheltenham Grammar School and Christ's College, London. He was then a training apprentice with the Outward Bound Sea School and left home to work as a deckhand in the merchant marine. He began his career in journalism as a reporter on a weekly newspaper in 1949. He moved to Fleet Street after two years of national service. He worked for the Daily Mirror, becoming a foreign correspondent in the New York bureau.
In 1960 he moved to television as a reporter on ITV's This Week current affairs programme, where he stayed for five years until joining the BBC.
He was co-editor and presenter of the landmark Man Alive series in 1965. He later formed the Man Alive Unit as well as providing the distinctive voice-over in the weekly current-affairs programme TEMPO directed by Mike Hodges.
In an interview in 1986 he said:
Real life honestly portrayed is sufficiently dramatic in itself. The idea that might lurk in some people's minds that you somehow have to beef it up, or pump it up or invent the circumstances to make it more colourful, is an idea born of Fleet Street and ignorance.
From 1972 to 1980 he was head of general features at the BBC. He made series including Americans, The Visit, Black in Blue and A Day in the Life.
After he left the staff of the BBC, Wilcox was involved in the occasional series following the story of David Jackson (David Lopez) 'the Boy David', a badly-deformed Peruvian boy (a sufferer of noma) whose face was rebuilt by a Scottish surgeon who adopted him. The series won six international awards.
He was married to television presenter Esther Rantzen in 1977 following an eight-year affair with her. They had three children together, including television presenter Rebecca Wilcox. He had three other children from an earlier marriage to Patsy, whose names were Claire, Adam and Cassandra. Claire had two children, Ruby and Martha. Cassandra had three, Rosie, Archered and Drew. He died of a heart attack in Paddington, London, in 2000, aged 69. He converted to Judaism in 1992.
- Esther Rantzen, The Autobiography, BBC Worldwide, 2001