Book: Between Silk and Cyanide by Leo Marks

Excellent personal memoir of a British cryptographer during the second world war

November 16, 2011

Leo Marks

Between Silk and Cyanide: A Codemaker’s War, 1941-1945

Free Press, 2000

ISBN-10: 0-684-86780-X

ISBN-13: 978-0-684867-80-9

624 pages

$23.99 (Kindle edition, $13.99)

Leo Marks’s father was half-owner of Marks & Co, an antiquarian bookshop at 84 Charing Cross Road in London. So it’s not particularly surprising that he grew up with a head for words. As a young man he earned pocket money creating cryptic crossword puzzles for The Times. He also seems to have had a head for numbers because he was interested in codes from a young age. In 1942, a godfather at Scotland Yard got him an interview with a government code-breaking school and he was accepted. That school routinely sent its graduates to Bletchley Park, but Mr Marks was a bit more independent-minded than the school’s administration liked, so they packed him off to a dodgy outfit called SOE. Inside ten months he was in charge of their codes.

Alas, being in charge of codes there sounds better than it was. Because the codes that SOE and its agents in occupied Europe used were very bad (a double transposition cipher based on a memorized text) and Mr Marks had a great deal of difficulty persuading his superiors that an improved code was a critical necessity. (The Free French code was worse, but that’s no consolation.) Among other things, Mr Marks invented one-time pads (they had been independently invented earlier) and he wanted them printed on silk for ease of concealment in the linings of agents’ clothes. Silk was in short supply of course, but Mr Marks impressed on his bosses that they would need to provide agents with either silk or cyanide.

If playing politics in his own department and with rivals at SIS weren’t enough, the Free French were just about as touchy as you’d suppose. Mr Marks was often in fear of losing his job. But in the end he made even the Free French happy.

Mr Marks was very good at his job but, working virtually alone (and with only very occasional consultations with Bletchley Park), he wasn’t really aware how good. And he was his own harshest critic.

Mr Marks instituted procedures for attempting to crack messages had been received that were indecipherable. When they could be cracked (which eventually was quite often) that saved the agent re-transmitting the message and gave the Germans’ direction-finding vans that much less time to find the transmitter.

And at one point Mr Marks’s unconscious mind seemed to find something a bit odd about the Dutch traffic (Freud had been in his father’s shop a few years earlier looking for books on Moses) but his conscious mind had some trouble figuring out what it was.

Many of the people Mr Marks worked with are fascinating and famous. Patrick Leigh-Fermor, Wing Commander F. F. E. Yeo-Thomas, Noor Inayat Khan, and Violette Szabo are among them. He worked with agents on the Norwegian heavy-water sabotage mission Grouse and well as operations Torch and Overlord, of course.

This passage is a bit more dramatic than most, but it gives a bit of the flavor of the book (Yeo-Thomas’s code-name was White Rabbit):

    On the night of 15 November the White Rabbit returned to England by Lysander

    with a female member of the French Resistance sitting on each knee

    (accommodation was strictly limited).

    The three of them had already become closely acquainted as they’d travelled

    to their pick-up point in the back of a hearse. Unaccustomed to this form of

    transport, Tommy had prepared for all eventualities by arming himself with a

    sten-gun, hand-grenades, and a bottle of brandy. The hearse had been stopped

    several times by German soldiers, who examined the undertaker’s credentials

    but not the state of his corpses. (p. 424)

Lest we find any of this too romantic, Mr Marks tells us that the average lifespan of a clandestine radio operator in occupied France was six weeks. Still, many of the troop trains bringing reinforcements to repel the allied D-Day landings in Normandy were derailed on the way to the front.

Anyone who has an interest in the geeky aspects of the history of the second world war will want to read this book. There are even a couple of code-making secrets that (as of the year 2000) Mr Marks was still not allowed to reveal.

There are a few things that Mr Marks might have explained a little more thoroughly (at least for us Yanks). And if you want to know about the actual mechanics of ciphers, you’ll want to read a book such as Simon Singh’s very excellent The Code Book, quite possibly before reading this one. But anyone who wants to read this book probably has already read that one.

I read this book on my Kindle and there are a fair number of formatting errors that, it seems, were introduced in creating the Kindle edition. But not enough of them to impair my enjoyment of the book.