He was born Nigel Marlin Balchin in Potterne, Wiltshire to William and Ada Balchin. He was educated at Dauntsey's School and Peterhouse, Cambridge, where he took a scholarship and became a Prizeman in Natural Sciences. He then worked for the National Institute of Industrial Psychology between 1930 and 1935, becoming a consultant to JS Rowntree & Sons, where he was intimately involved in the design and marketing of Black Magic chocolates. and, he claimed, responsible for the success of the Aero and Kit Kat brands.

He wrote for Punch magazine, published as Mark Spade, and also wrote novels under his own name. During World War II he was a civil servant at the Ministry of Food, and then a successful scientific adviser, rising to the rank of Brigadier.

In 1956, he moved abroad to write screenplays in Hollywood and elsewhere, but was increasingly troubled by alcoholism, and returned to England in 1962. He died in 1970 at a nursing home in Hampstead, London, and is buried in Hampstead Cemetery.

His novels enjoyed great popular success for a time. Darkness Falls From the Air is set during the London Blitz and was written while the bombing was still in progress. The Small Back Room became a Powell and Pressburger film. A Way Through the Wood was adapted as a stage play Waiting for Gillian, and as the 2005 film Separate Lies.

As a screenwriter he worked on an early draft of Cleopatra but is principally remembered for The Man Who Never Was, for which he won the 1956 BAFTA Award for Best British Screenplay, and Mandy, the story of a deaf child.

Balchin was married twice, firstly to Elisabeth Evelyn Walshe (1910—1991, daughter of the novelist Douglas Walshe) whom he had met at Cambridge where she was reading English at Newnham. m. 1933, div 1951 with children:

Prudence Ann Balchin (born 1934)

Penelope Jane Balchin (born 1937) , better known as childcare expert Dr Penelope Leach

Freja Mary Balchin (born 1944)

His first marriage broke up following a partner-swapping arrangement between the Balchins, the artist Michael Ayrton and the latter's partner Joan. Elisabeth divorced Balchin to marry Ayrton in 1952.

He married secondly Yovanka Zorana Tomich m. 1953 , with children:

Charles Zoran Marlin Balchin (born 1955)

Cassandra Marlin Balchin (born 1962)

Nowadays, Yovanka uses the name Jane . All his children have enjoyed successful careers.

From his first marriage:

• Prudence married 'Z Car' scriptwriter John Hopkins and ran a successful zoo for many years.
• Penelope married the noted science journalist Gerald Leach (1933—2004), and became arguably the world's foremost childcare expert
• Freja became the first female president of Cambridge University's Student Union and married Richard Gregory, a leading psychologist.

From his second marriage:

• Charles is a leading figure in the world of sport and television having held senior roles at the BBC, Sky Sports and various overseas broadcasters
• Cassandra is one of the most sought-after authorities on women's rights under Islamic law.

Books by Mark Spade

• How to Run a Bassoon Factory; or Business Explained (1934)
• Business for Pleasure (1935)
• Fun and Games - How to Win at Almost Anything (1936)
• How to Run a Bassoon Factory and Business for Pleasure (1950)

Novels by Nigel Balchin

• No Sky (1934)
• Simple Life (1935)
• Lightbody on Liberty (1936)
• Darkness Falls from the Air (1942)
• The Small Back Room (1943), made into a film in 1949
• Mine Own Executioner (1945), made into a film in 1947
• Lord, I Was Afraid (1947)
• The Borgia Testament (1948)
• A Sort of Traitors (1949), made into a film in 1960
• A Way Through the Wood (1951), made into a stage play Waiting for Gillian, and the 2005 film Separate Lies.
• Sundry Creditors (1953)
• The Fall of the Sparrow (1955)
• Seen Dimly Before Dawn (1962)
• In the Absence of Mrs. Petersen (1966)
• Kings of Infinite Space (1967)

Screenplays by Nigel Balchin

• Fame is the Spur (1947)
• Mine Own Executioner (1947)
• Mandy (1952)
• The Malta Story (1953)
• Josephine and Men (1955)
• The Man Who Never Was (1955)
• The Leader of the House (written for TV 1955)
• 23 Paces to Baker Street (1956)
• The Barbarian and the Geisha (not credited 1958)
• The Blue Angel (1959)
• Suspect (1960)
• Circle of Deception (1960)
• The Singer Not the Song (1961)
• Barabbas (1961)
• The Hatchet Man (written for TV 1962)
• Cleopatra (not credited 1963)
• Better Dead (written for TV 1969)

Miscellaneous

• Income and Outcome (1936)
• The Aircraft Builders (1947)
• The Anatomy of Villainy (1950)
• Last Recollections of My Uncle Charles (1954) stories
• The Worker in Modern Industry (1954)
• Fatal Fascination (1964) essays by Balchin and three other writers