The Thirty-One Kings and Castle Macnab, by Robert J. Harris, purport to be the beginning of a new series called "Richard Hannay Returns' about his adventures during World War II. In Combined Forces, a humorous novel by Jack Smithers, Hannay teams up with the similar heroes "Sapper"'s Bulldog Drummond and Dornford Yates' Jonah Mansel.
As revealed through the various novels, Richard Hannay was born in Scotland about 1877; his father was Scottish and had German business partners. He was brought up to speak German pretty fluently. At the age of six he joins his father in South Africa. He becomes a mining engineer, spending three years prospecting for copper in German Damaraland and makes a small fortune in Bulawayo. He takes part in the Matabele Wars, serves two years with the Imperial Light Horse and serves as an intelligence officer at Delagoa Bay in the Boer war. He goes to England in 1914, shortly before the events of The Thirty-Nine Steps. The First World War breaks out eight weeks after the events of The Thirty-Nine Steps, and Hannay immediately joins the New Army, and is promptly commissioned captain on the strength of his Matebele campaign experience. He is wounded in the leg and neck in the Battle of Loos in September 1915, by which time he had reached the rank of major. Greenmantle, the sequel to The Thirty-Nine Steps begins in late 1915, with Hannay in Hampshire where he has arrived to convalesce after Loos. During the events of Greenmantle, his work as a spy in wartime Europe and Turkey earn him a DSO and CB, respectively. Following this, he returns to regular service in the army and is rapidly promoted to brigadier-general. In early 1917, however, he is called back to the Secret Service to hunt a dangerous German spy during the decisive months of the First World War. As told in Mr Standfast, he meets and falls in love with Mary Lamington, an intelligent, beautiful young nurse and fellow spy. Later, in 1918, now promoted to major-general, he returns to the front lines and participates in desperate fighting following the Germans' massive, last-ditch effort to win the war. Soon after the end of the war, Hannay marries Mary Lamington, and the following year they have a son, Peter John Hannay. The boy is named after Hannay's two great friends John Scantlebury Blenkiron and Peter Pienaar, an old Boer scout who seems to have been a kind of father-figure to him. The family settles in Mary's old home in the Cotswolds, Fosse Manor, Oxfordshire and Hannay finds peace and enjoyment as a farmer. However, in 1920 or 1921, Hannay again finds himself in an adventure, this time with his wife's help unravelling a kidnapping mystery in The Three Hostages. His last adventure, The Island of Sheep, occurs some 12 years later when Hannay, now in his fifties, is called by an old oath to protect the son of a man he once knew, who safeguards the secret of the greatest treasure on earth. This book also focuses on Hannay's son, Peter John, now a bright but solemn teenager. Though the Hannay books stop short of the Second World War, Buchan's last novel, Sick Heart River offers a hint about Hannay's future: dying in Canada, Hannay's friend Sir Edward Leithen hears of the outbreak of war in Europe and guesses that many of his old friends, including Hannay, will have taken up arms again.