Born Trevor-Dudley Smith in Bromley, Kent, he lived in Spain and France before moving in 1973 to the United States, where he lived in Phoenix, Arizona. He was married and had a son. He was proficient in karate.

Writing

The Quiller series focuses on a solitary, highly capable spy (named for Sir Arthur Quiller-Couch) who works (generally alone) for a government bureau that "doesn't exist" and narrates his own adventures. Quiller (not his real name) occupies a literary middle ground between James Bond and John le Carré. He is a skilled driver, pilot, diver, and linguist, but does not carry a gun.

The series is very stylized, featuring intense depictions of spy tradecraft and professional relationships, surprising jump cuts between chapters, and deep, sometimes self-pitying interior monologues. The first of the Quiller novels, The Berlin Memorandum (1965) (retitled The Quiller Memorandum in the US) won an Edgar Award, from the Mystery Writers of America, for Best Novel. It was filmed in 1966 under its US title and starred George Segal and Alec Guinness. It was also adapted into a 1975 British television series, featuring Michael Jayston.

As "Simon Rattray," he wrote mystery novels featuring Hugo Bishop, a brilliant man who, like Agatha Christie's Hercule Poirot, solved crimes as a kind of mental challenge. The first Bishop novel, Knight Sinister, appeared in 1951; five more followed, the last appearing in 1957. That Trevor could also be very effective in the straight, non-mystery genre is shown by The Billboard Madonna (1961): the protagonist accidentally kills a beautiful woman in a car crash, and is obsessively compelled to memorialize her.

Under the name "Adam Hall," he also wrote "The Volcanoes of San Domingo" about a mysterious plane crash off the coast of San Domingo and the efforts to uncover what really happened. When alerted by a report indicating that one of the crew members had been seen alive, "Rayner," an employee of the airline, is sent to investigate.

He also wrote children's book about the character "Wumpus", a koala bear, and his friends, including Flip Flap, the penguin. Titles included Wumpus (published 1945, by Gerald G. Swan), and More about Wumpus (published 1947).