After completing his two years of National Service, 1951 to 1953, as a Pilot Officer in the Royal Air Force flying Gloster Meteors, he went to Pembroke College, Cambridge, graduating in 1956 with honours in English.

While at Cambridge he wrote regularly for the undergraduate newspaper Varsity and also created a strip cartoon whose hero, "Olly", reflected student life and became a cult figure.

After graduating he worked briefly as a reporter for the Birmingham Gazette, Picture Post and Sunday Graphic newspapers and then as a film director for the BBC's Tonight programme.

The aviation thrillers (The Wrong Side of the Sky, The Most Dangerous Game, Shooting Script, and Judas Country), and what might be called "Euro-thrillers" revolving around international crime in Europe (Midnight Plus One, Venus With Pistol, and Blame The Dead).

Despite the commercial success of his work, Lyall began to feel that he was falling into a predictable pattern, and abandoned both his earlier genres, and the first-person narrative, for his "Harry Maxim" series of espionage thrillers beginning with The Secret Servant published in 1980.

This book, originally developed for a proposed BBC TV Series, featured Major Harry Maxim, an SAS officer assigned as a security adviser to 10 Downing Street, and was followed by three sequels with the same central cast of characters.