Nicholas Evans, who has died aged 72 after a heart attack, was the unlikely author of the bestselling novel The Horse Whisperer (1995), which became a Robert Redford film. Unlikely because the book, set in Montana, was a first novel by a British television producer, and landmark because the book sold for a record price at auction, and justified its sale price.

Evans had previously left a successful position as number two to Melvyn Bragg on the South Bank Show, where he produced many of the flagship programmes of the television arts series, including profiles of Patricia Highsmith, John Le Carré, Laurence Olivier, Francis Bacon and, most crucially, the film director David Lean, who became a friend and wondered why Evans was making a film about him, and not something he wanted to do for himself.

Evans then co-produced and wrote a TV film, Murder By the Book (1987), about Agatha Christie and her character Hercule Poirot, played by Peggy Ashcroft and Ian Holm. He wrote three screenplay adaptations, but by 1993 a film project had fallen through and he found himself £65,000 in debt and diagnosed with a stomach melanoma.

Evans had begun writing a novel based on a story that he had been told by a Devon blacksmith, who used the term “horse whisperer” to describe someone with a gift for communicating with horses. Evans had gone to the US, to meet men who did this, thinking the story needed a western setting. “If you set a book in postwar or contemporary Britain, something shrinks,” he said. “It becomes parochial.”

He gave the manuscript of the book, half-finished with an outline of the remainder, to his friend the agent Caradoc King, who took it to the 1994 Frankfurt book fair, where it instigated a bidding war.

Dell bought the US rights for $3.15m, Bantam got UK rights for $537,000 and translation deals in Germany and Italy netted another million dollars. The film rights went to Robert Redford for another $3m because Evans saw Redford in the role of his hero, Tom Booker.

While this was happening, his melanoma was removed by surgery and his local bank manager, who had been demanding repayment of his overdraft, called and invited him to lunch.

The novel got mixed reviews, especially in the US. Virtually no critic could resist mentioning Evans’ advances; many also drew comparison with Robert James Waller’s The Bridges of Madison County. Evans himself acknowledged the influences of Cormac McCarthy, Ernest Hemingway and Jack London. The New York Times critic Michiko Kakutani called it “a sappy romance novel, gussied up with some sentimental claptrap about the emotional life of animals and lots of Walleresque hooey about men and women”.

But it shot to the top of the New York Times’ bestseller list, ranked No15 for the year despite being released in the autumn, and remains one of the bestselling novels of all time. Redford’s 1998 film, which starred the 14-year-old Scarlett Johansson as Grace, the teenager injured along with her prize horse, and Kristin Scott Thomas as her mother, who seeks out Redford’s Booker, and has an affair with him, did well but was not a huge hit.

Evans was born in Bromsgrove, Worcestershire, the son of Anthony, the sales director of a motor engineering company, and Eileen (nee Whitehouse). He was head boy at Bromsgrove school, and after a year teaching in Senegal for Voluntary Service Overseas, went to St Edmund Hall, Oxford to study law, where he met Jenny Lyon, his future wife, in their first week.

After taking a first-class degree, he started work as a journalist for the Evening Chronicle in Newcastle. In 1975, he started at London Weekend Television, first on Weekend World and then the London Programme, the broadcaster’s top current affairs show, before joining the South Bank Show as executive producer from 1982 to 1984.

After Murder By the Book, he adapted screenplays for the TV movies Acts of Betrayal (1988), about the IRA, and Secret Weapon (1990), the story of Mordechai Vanunu, the nuclear bomb whistleblower kidnapped by the Israelis and imprisoned for treason, and for the Julie Walters film Just Like a Woman (1992), based on Monica Jay’s novel about a transvestite’s romance with his landlady.

His second novel, The Loop (1998), brought a wolf biologist, Helen Ross, from Cape Cod into Yellowstone Park to cope with the reintroduction of wolves; pursued by a local lothario, she instead romances his 18-year-old son and cures his stutter. It sold 5m copies.

He followed this up with The Smoke Jumper (2001), whose titular protagonist is in love with his best friend’s wife, and who exiles himself as a war photographer. Next came The Divide (2005), about a wealthy New York couple who holiday in Montana, where the body of their eco-terrorist daughter is discovered frozen in the mountain ice.

Evans and Jenny divorced in 1998. He then married the singer-songwriter Charlotte Gordon Cumming. In 2008, while on a visit to Gordon Cumming’s brother’s estate in Scotland, Evans picked mushrooms for a family lunch. What he thought were ceps were instead highly poisonous webcaps. Evans, Gordon Cumming and her brother were all placed on kidney dialysis. Three years later, Evans’ heart began to suffer under the strain of dialysis, and his daughter Lauren provided him with a kidney; Gordon Cumming later received one donated from a friend.

At the time of the poisoning, Evans had almost finished his fifth novel, The Brave (2009), about a family’s hidden secrets.

When he began writing again, thinking for the second time he needed to finish writing before he died, he said the book changed direction. “I found new empathy with the characters ... it became more emotional,” he said. Gordon Cumming released an album of songs tied to the novel, and they campaigned together for kidney care and organ transplants.

The couple lived in a 14th-century manor house in Devon once owned by the film director Robert Bolt.

Evans is survived by Charlotte, their son, Finlay, his children Lauren and Max from his first marriage, and by Harry, his son from a relationship with the television producer Jane Hewland.

• Nicholas Benbow Evans, writer and television producer, born 26 July 1950; died 9 August 2022

• This article was amended on 22 August 2022. Evans’ daughter Lauren is from his first marriage, rather than his second, as the original stated.