The welcome release by the National Archives over the last decade of a huge batch of wartime files from the Security Service (MI5), and the availability of previously secret documents from other agencies such as the Special Operations Executive – now matched by the publication of the ‘official histories’ of MI5 and the Secret Intelligence Service (MI6) – has led to the publication of a growing number of intelligence-related biographies and histories. Some are very good, but often the reliance on the files at Kew has led to lazy research and publications that are little more than histories of the files (which mostly have been weeded and should be treated as unreliable and self-serving) rather than histories of an event or organisation. Christopher Andrew’s history of the Security Service, which used openly published material to flesh out the anonymous files, was a success; but Keith Jeffery’s history of the Secret Intelligence Service, which relied totally on the Service’s still-secret registry files, illuminated very little. Sometimes it takes a journalist to identify what is interesting and dig out that extra piece of research that makes a book worthwhile.

Retired Daily Mail journalist Peter Day has produced an admirably short book primarily based on recently released files at the National Archives, which he has supplemented with other sources. He has managed to pull together a wonderful tale of British Catholic eccentrics, intelligence agents from the 1930s world