by Catherine Flinn

Although the literature on Second World War code-breaking, Bletchley Park, Enigma and Alan Turing and his peers is prolific, Dilly is a significant contribution to the existing scholarship. Mavis Batey is a former code-breaker who worked at Bletchley Park quite closely with her subject, Alfred Dillwyn Knox (1884-1943). However, the book is not – and does not read as – memoir. Rather, this is a noteworthy analytical work in its own right: it is well-written, thoughtful and thoroughly researched.

It is likely that there is no better author to have taken on the challenge of presenting the life and work of Knox, who has been both under-appreciated and overlooked. Mavis Batey was hired to work in the Government Code and Cipher School at the beginning of the war. Soon after, she was sent to Bletchley Park to work with Knox on breaking early Enigma messages. Batey worked with him until his death, in 1943, and continued to work at Bletchley Park until after the end of the Second World War.

The book successfully chronicles “Dilly” Knox’s important place in British history, documenting his ground-breaking work without over-glorifying his life, yet still giving proper credit where due. Readers are taken from his origins as a minister’s son who grew up solving logic problems, to his work as a Classics scholar with important publications in Greek literature, to the translation of that work into his interest in and talent for deciphering and code-breaking. Batey is able both to understand and detail his code-breaking theory and methodology. She also successfully contextualises Knox’s interest in the author, mathematician and logician Lewis Carroll (1832-1898), having published on the subject herself.

Although Alan Turing (1912-1954) has received most of the code-breaking acclaim, the reader comes to understand that Knox should have shared such recognition equally. Yet for many years - and still today - much of the relevant documentary evidence remains unavailable. Batey also provides a bigger picture, which highlights the importance of Dilly’s contributions to the war in general, from the British naval victory at Matapan to the role of code-breaking in the campaigns in North Africa and the Normandy landings.

Additional themes in the story continue to have contemporary significance: Dilly stressed the importance of sharing intelligence so that it got into the hands of those who needed it most and was useful. This same theme is in the forefront of today’s news, as the United States has admitted that security issues brought to light via the “Christmas Day bomber” (2009) resulted from a lack of cooperation within government intelligence organisations. Of current importance also is the ongoing science of encryption and decryption, used daily in modern communications, with scientists having recently demonstrated an ability to break mobile phone security. A final recurring theme is Dilly’s awareness – so often overlooked – that all the operators transmitting the coded messages were human, and made mistakes, and it was often the exploitation of these mistakes that gave the “way in” to getting a break.

Ralph Erskine’s introduction is very helpful if somewhat inflammatory: he is highly critical (though probably rightly so) of the British government’s over-classification and continued secrecy over documents, which could help set the record straight, rather than endanger current national security. The appendices – contributed by Ralph Erskine and Frank Carter – are a cryptanalyst’s dream and extremely helpful for anyone interested in the details of breaking Enigma. It would have been even more useful to have included photographs of the “rods” used, but this is a minor point.

The only real shortcoming of the book lies in the lack of scholarly sourcing. This is presumably not the author’s fault, since the editor is the journalist Michael Smith (who himself has published interesting work on both code-breaking and Bletchley Park), and the book is perhaps not intended to be used as a resource. Nevertheless, the hit-and-miss nature of the sourcing and style (no in-text numbers or notes) was very frustrating for an academic historian. Yet on the whole, this first publication off the new “press” of Dialogue is very impressive: historically significant and worthwhile reading for both historians, and anyone interested in problem-solving, code-breaking and certainly the Second World War.