Abstract
This article considers the extra‐judicial work of Lord Diplock in the domain of national security in the context of his life and judicial work. It first considers briefly the role of judicial biography in understanding the work of judges and then the particular considerations which apply to such biography in the context of national security law and practice. The following sections consider Lord Diplock's role in national security oversight, emphasising the wide range of issues with a national security dimension which Diplock was called upon to consider. It then seeks to shed light on the reasons for which he was repeatedly entrusted by the government to consider matters of the utmost sensitivity by turning back to his early life, his service during the second world war, and his work thereafter.