Protagonists who assume new identities, often because they are transplanted into foreign cultures, are a recurring element in Llewellyn's novels, including a spy adventure that extends through several volumes.

Late in his life, he lived in Eilat, Israel. Following the war, he worked as a journalist, covering the Nuremberg Trials, and then as a screenwriter for MGM. During World War II, he rose to the rank of Captain in the Welsh Guards. Before World War II, he spent periods working in hotels, wrote a play, worked as a coal miner and produced his best known novel. He lived a peripatetic life, travelling widely throughout his life. It immortalised the way of life of the South Wales Valleys coal mining communities, where Llewellyn spent a small amount of time with his grandfather. Several of his novels dealt with a Welsh theme, the best-known being How Green Was My Valley (1939), which won international acclaim and was made into a classic Hollywood film. Davids, West Wales was false, though of course he was of Welsh blood. Only after his death was it discovered that his claim that he was born in St. Llewellyn was born of Welsh parents in Hendon, north London in 1906. Before World War II, he Richard Llewellyn (real name Richard Dafydd Vivian Llewellyn Lloyd) was a British novelist.

Richard Llewellyn (real name Richard Dafydd Vivian Llewellyn Lloyd) was a British novelist.

Llewellyn how green was my valley