John le Carré: The Spy Who Came in From the Cold (1963)
Eric Ambler: Epitaph for a Spy (1938)
Eric Ambler: Journey into Fear (1940)

On the cover of my old paperback of The Spy Who Came in From the Cold is a quotation from JB Priestley’s review: “Superbly constructed with an atmosphere of chilly hell.” Both are true of one of the greatest spy novels ever written and the book with which the little-known young Le Carré, who had himself served in MI5 and was working for MI6 at the time of publication, superseded Eric Ambler, the author who had revolutionised spy fiction in the late 30s. Le Carré’s story of Alec Leamas, a hardened cold war foot soldier who has lived “without sympathy”, starts and ends at the Berlin wall. In the last operation before he comes in from the cold, Leamas is persuaded by Control and George Smiley to defect to the east and to incriminate Hans-Dieter Mundt, apparently the Circus’s archenemy. Leamas is the poisoned pill, but only in last pages of the book does he realise that he has been used in an elaborate double bluff and that his true mission was to protect Mundt. It is all so cleverly worked - Leamas’s descent, then his redemption through love for the librarian Liz Gold, the court scenes in East Germany and the final agonising dash for the border. The plot is said to have been based on a real operation in Czechoslovakia, although I have never seen le Carré confirm this. Even if it is true, the book’s power comes not from reported actuality, but from le Carré’s quality as a novelist and his understanding of the treachery involved in the cold war and the moral ambiguities of the ideologies on both sides.

Le Carré owes something to Ambler, who rescued the spy novel with a succession of titles just before the war from what one critic has described as the “congenital Tories” (William Le Queux and Edward Oppenheim). Left-leaning and profoundly critical of Britain’s insularity in the 30s, Ambler was often at his best in the closed-world novels such as Epitaph for a Spy which takes place in a hotel in the south of France, where the Hungarian hero Vadassy finds himself in the midst of a fascist spy ring, and Journey into Fear, his last book before the war. This is the most psychological of his novels and has the English hero Graham, an expert in the Turkish military who is insular, conventional and politically naive, on a boat being pursued by Nazi assassins. Ambler never confronted the cold war, never took sides because he found it “distasteful”. He continued writing, but in the political sense opted for voluntary obsolescence, which Le Carré avoided when, in 1989, the wall where Leamas had been sacrificed fell down.

• Henry Porter is a novelist and columnist for the Observer