[Len Deighton], with no war experience, but with knowledge of investigation tactics as well as military history,… uses this background [in The Ipcress File] to good advantage in a tale of espionage. Unlike the straight intelligence work of Ian Fleming or our own Van Wyck Mason, Deighton writes with a tongue-in-cheek attitude. The action, brutality, deaths and the slight bit of romance which is allowed to seep into such stories, are all present; but so are the weaknesses of our C.I.A., Scotland Yard and various other agencies. No one is spared the needle of subtle ridicule, but the author still tells a plausible story which holds your attention throughout. (p. 302)

John B. Cullen, "Fiction: 'The Ipcress File'," in Best Sellers (copyright 1963, by the University of Scranton), Vol. 23, No. 16, November 15, 1963, pp. 301-02.