Aka Gavin Black

From Wikipedia:

Oswald Wynd (1913 – 1998) was a Scottish writer, born in Tokyo of parents who had left their native Perth to run a mission in Japan.
He attended schools in Japan where he grew up speaking both English and Japanese. In 1932 he returned with his parents to Scotland, and studied at the University of Edinburgh and began to write novels. When World War II came he joined the Scots Guards but was then commissioned into the Intelligence Corps and sent to Malaya. At the time of the Japanese invasion, he was attached to the Indian Army on the east coast of Malaya, and his brigade covered the final withdrawal to Singapore. Cut off by the Japanese advance, he was lost alone for a week in the Johor jungle. Eventually he was captured and spent more than three years as a prisoner of war, during which time he was mentioned in dispatches for his work as an interpreter for prisoners.
In Hokkaidō, during the last year of the war, he began a novel, Black Fountains, which in 1947 won the Doubleday Prize.[1][2]
After the war he returned to Scotland, via the Philippines, having now spent some twenty-three years of his life in the Far East. He lived in Scotland until his death in 1998 writing, among other books, the much admired The Ginger Tree and a series of highly successful thrillers under the pseudonym of 'Gavin Black'.
In the late 1980s The Ginger Tree was turned into a television series by the BBC, with NHK, Japan and WGBH Boston [3][4], starring Samantha Bond as the protagonist.