Book Review: Between Silk and Cyanide, by Leo Marks

We have a little time left
The wise doctor said
Unless there’s a miracle
Which is another man’s trade

Selfish as always
I’ve started missing you now
Want to say so
Don’t know how
Want to hug you
Don’t know if I should
Hope you understand
I’d take your place if I could

In 1942, at the age of 22, Leo Marks joined the secret British agency known as Special Operations Executive, and soon became the organization’s Codemaster, responsible for the security of communications with SOE’s resistance and sabotage agents in occupied Europe. He usually briefed these agents…soon-to-be-legendary individuals like Violette Szabo and Forest Yeo-Thomas…before their departures and they all left indelible impressions on him. His memoir is a very emotional book: frequently heartbreaking, sometimes very funny. There is a lot about the technical aspects of cryptography, but these sections can be skipped or skimmed by those who are primarily interested in the powerful human story. Poetry, much of it written by Marks himself, played an important part in SOE’s cryptographic operations and hence plays an important role in this book.

When Marks joined SOE, communication with agents was accomplished using a poem code. Each agent chose a poem and memorized it precisely: a copy was retained at SOE headquarters. When the agent wished to send a message–a very hazardous operation, as the Germans maintained a large network of radio direction finders–he or she would mathematically combine the letters of the message with the successive letters of the poem. The process would be reversed at the other end, yielding–if all went right–the clear text. But if the agent made a single mistake in the encoding, the message would probably be un-decipherable, and the agent would be required, at great personal risk, to retransmit it. Marks found this to be disturbing and unreasonable:

If (a wireless operator in occupied territory), surrounded by direction-finding cars which were after him like sniffer dogs, who lacked electric light to code by or squared paper to code on–if that agent hadn’t the right to make mistakes in his coding without being ordered to do the whole job again at the risk of his life, then we hadn’t the right to call ourselves a coding department.

His resolution to do something about this problem became definitive after he briefed “my first frightened agent.”

When Paul and I shook hands they needed galoshes…He suddenly asked what would happen if he made ‘a bit of a mistake’ and sent us a message we couldn’t decode.

I didn’t want him to know that he’d be dependent on me. I improvised a little and told him that we had a team of girls who’d been specially trained to break indecipherable messages…I then asked him to run through his poem for me and took out his code-card to check the wording. He shyly admitted that Tennyson’s ‘In Memoriam’ was his favourite poem…He was silent for a few moments and then whispered the words–I wasn’t sure to whom:

Be near me when my light is low
When the blood creeps, and the nerves prick
And tingle; and the heart is sick
And all the wheels of being slow.

I was careful to keep looking at the code-card. There was nothing more that I could say to him. But there was one thing that I could do.

Marks went to the Grendon wireless station to meet the girls who worked as code clerks and to begin the task of training them for the much more difficult work of breaking indecipherable messages. It was only two days later that he received a message on the teleprinter:


Another huge problem with the poem-code was that it was potentially very insecure: if the Germans could guess the poem being used, they could readily decode the message…with adequate resources, they could try hundreds of poems against each message until they found the key that fit the lock. Marks reasoned that if poems that had never been published anywhere could be used instead of the old standards, the task of the enemy could be made much more difficult. He began writing poems when the inspiration struck him (the poem quoted at the beginning of the post is one example of his work) and encouraged the coders of Grendon (known as FANYs because they were members of a paramilitary organization called the Field Auxiliary Nursing Yeomanry) to do the same. One day the female brigadier who supervised the FANYs walked into a room where a dozen of her charges were quietly and totally absorbed in “the ladylike pursuit of composing poems.” Unfortunately, she picked up an example of their work, which began:

Is de Gaulle’s prick
Twelve inches think

When the brigadier’s complaint reached Marks, he responded that the poem was excellent: the imagery was unusual, the words easy to memorize, and the content not at all what the enemy would be expecting.

Shortly before an agent departed for enemy-held territory, Marks met with him/her to review the selected poem and the coding procedures. He was well aware that many of these agents would not be coming home. Each agent was given the option to carry a lethal pill (the “cyanide” in the title of the book) to be taken–if there was time–in the event of capture. Some of these agents were…

Noor Inayat Khan, the Indian-American daughter of a leading Sufi mystic and a writer, particularly of children’s books. (One of her books is still in print.) She had abandoned the pacifist principles taught by her father in order to join the fight against Naziism. Marks describes his first meeting with her:

I longed to be able to walk into a briefing room and switch on the detached receptivity with which an analyst treats his patients…But as soon as I glimpsed the slender figure seated at a desk in the Orchard Court briefing room I knew that the only thing likely to be detached was one (if not both) of my eyeballs. No one had mentioned Noor’s extraordinary beauty.

After the briefing, Noor departed for France by light plane. After serving the Resistance as a radio operator and evading capture several times, she was eventually caught by the Gestapo and killed.

Francis Yeo-Thomas, who before the war had been general manager of the Molyneux fashion house in Paris. One of SOE’s leading agents, “Tommy” made many trips back and forth to Occupied France, and he and Marks became well acquainted. The much-younger Leo Marks asked for Tommy’s advice often, and admired him unreservedly. “I had never met anyone I trusted so completely or whose trust I valued more.” Marks remembers Tommy congratulating him on his promotion and putting his hand “firmly on my shoulder.” Writing 50 years later, Marks adds “It’s still there, Tommy. Hope you know it.”

Marks recalls a strange and disturbing dream in which Tommy appeared, along with Churchill, Tommy’s girlfriend Barbara, and two kinds of codes known as WOKs and LOPs:

I dreamed that Churchill was in danger of dying, and that Tommy was stating his case to God. Tommy offered the Lord a WOK, and then a LOP, and then himself, if Churchill could be spared. Christ and Moses were present as members of the Executive Council. Barbara was taking notes, and I was holding a copy of the FFI code-book in case Jehovah wanted that too. “No,” said Barbara, “Tommy’s life will be enough,” and a tear fell on her notebook. A heavenly choir began chanting “Hosanna” in Morse.

Violette Szabo, who struck Marks as “a dark-haired slip of mischief” on their first meeting. She had problems remembering the French nursery rhyme she had been given as a code poem, and Marks suggested as an alternative a poem he had written himself…although he never told her that he was the author. The poem, “The Life That I Have,” later became well-known after its inclusion in the movie which was made about Violette in 1958.

She carried out two missions into France…on the first one, she celebrated her success by treating herself to a shopping expedition in Paris. On the second mission, she twisted her ankle while running from German troops, and held the enemy off with her submachine gun while her partner made his escape. She was captured and executed: her George Cross award for bravery was presented by the King to her daughter Tania.

Francis Cammaerts, like Noor a pacifist who had reconsidered his views. Marks found Cammaerts to be a very frustrating student of coding methods: he finally realized that his pupil was constitutionally unable to mechanically conduct a series of operations for which he did not understand the underlying reasons–once Marks explained the theory behind the coding to him, Cammaerts did just fine. Which was fortunate, because Cammaerts became one of SOE’s most important and successful agents, organizing resistance activities in the south of France on a large scale.

I met Mr Cammaerts in the summer of 2001, and in a future post will have much more to say about this interesting and noble man.

Despite the improvements brought about by the unique poems and the growing cadre of girls dedicated to breaking “indecipherable” messages, Marks remained frustrated with the poem-code approach. He lobbied for an approach based on a one-time pad: a code to be inscribed on a piece of silk and with each element used only once. Such a code was theoretically unbreakable by cryptographic means: moreover, it could not be memorized (being a random string of letters) and hence could not be tortured out of a captured agent. Why silk? For one thing, it burns very quickly. Much of the book deals with the political maneuvering that was necessary to get the silk codes adopted and the necessary materials produced in large quantity. The poem-codes were still retained as a backup, for cases where the silk was lost. The SOE poem-code project continued throughout the war. Here’s another Marks creation that I like:

Have you never known
A glass-bottomed day
When your minutes can be seen
Flowing beneath you
In every direction
But the one you mean?

Have you never known
A winterproof night
When wrong feels right
When the heart’s chill
Is a matter of will

And mother’s pride
Is safe inside
An envelope of ice
And doesn’t even hear
A cock crow thrice?

Marks was often inspired to commit poetry when meeting a new colleague…especially if the colleague was someone he instinctively disliked. After meeting a Signals administrator named Miss Saunders, he wrote:

A long line of lips
The eyes an eclipse
Arteries hardened
Nobody pardoned
Who holds the key
To that self-locking face
Who stole your grace?

(Despite this inauspicious start, Marks and Miss Saunders soon became friends.)

Marks often enjoys laughing at his younger self. He observed that even the girls who were the best, most consistent coders occasionally went through times when their error rates increased substantially. Analyzing the data, he “sensed a pattern to the lapses which I couldn’t define.” He asked for help from Captain Henderson, an attractive Canadian woman who was personnel officer for the FANYs. Marks described the error problem, and Captain Henderson suggested that it might have something to do with periods. After realizing that the naive Mr Marks had no idea what she was talking about, she directed her secretary to hold all calls for the next half hour while she educated the Codemaster in the basic facts of female biology.

Though the book is leavened with much humor, the heartbreak is never very far away. Just about the time of the German surrender, Marks noticed “an old man watching me from the doorway” of his office. He was about to ask the man if he an appointment, but then he realized…

It was Tommy. He had been in Buchenwald.

After the European war ended, SOE was quickly disbanded. Marks wandered through the empty offices, and on the wall he wrote one last poem:

We listen round the clock
For a code called peacetime
But will it ever come
And shall we know it when it does
And break it once it’s here
This code called peacetime

Or is its message such
That it cannot be absorbed
Unless its text is daubed
In letters made of lives
From an alphabet of death
Each consonant a breath
Expired before its time

Signalmaster, Signalmaster
Whose Commandments were in clear
Must you speak to us in code
Once peacetime is here?

I cannot recommend this book highly enough.

Some related links:

My post about Noor Inayat Khan
My post about Violette Szabo
Tania Szabo’s web site
The women of SOE

16 thoughts on “Book Review: <em>Between Silk and Cyanide</em>, by Leo Marks”

  1. David, thanks for this. I bought the book. Have you seen the movie about Violette Szabo? Is it any good? I went to Netflix and ordered it. I used to have a picture of Violette Szabo taped to the wall near my desk.

    I have the bio of Noor Inayat Khan but have not read it yet.

    I look forward eagerly to your post about Mr. Cammaerts.

    I recently watched Sophie Scholl: The Final Days. She was also brave, like the SOE women, and like them died at the hands of the Third Reich. But unlike them she was in no position to actually have an impact, since the Nazis were already in power and she was doomed the moment she crossed them. The trick is to prevent it from ever getting to that point.

  2. Pleasantly surprised that the Violette movie (“Carve her name with pride”) is now available on Netflix…I had to get it from the UK and then have it converted to US format. Yes, it’s definitely worth seeing, though it has some inaccuracies since SOE work was still pretty much in the dark when it was made (and there is a lot about SOE’s activities that will probably never be known.) Virginia McKenna (Born Free, Ring of Bright Water) does a fine job in the title role..she has said that playing Violette was a very intense emotional experience for her.

  3. I happened to find myself waiting for a flight once without anything to read. I walked into the airport magazine shop and did about a minute’s worth of browsing. Between Silk and Cyanide looked like the most interesting so I bought the paperback. I read it on the flight over, went to the hotel room and read it till it was finished. I’ve since gone back and re-read it. One of the luckier finds of my reading experience. It’s an excellent book and highly recommended. Nice portrait of the British Empire in its last days before we and the Labour Party euthanized it.

  4. Read this one last year. Yes, it’s good, and very human. You left out that the famous “The Life that I Have” poem was one Marks wrote during a period of black despair, when his fiancee was killed in a plane flight to Canada.

    I did not think the “Carve Her Name with Pride” movie was much good. Virginia McKenna did not make a convincing “dark-haired slip of mischief.”

  5. But there was one thing that I could do.

    I miss the point of this episode. So, what exactly did he do for that guy? What did he taught the “girls”? And why it took them “only two days” to decipher some message? How long did it take them before his instruction?
    It all sounds a bit strange…like a story without a punchline.

    I know programmers and generally people who use math in their professions love books and films about WWII coding (I vaguely remember a movie about Brits cracking some code or other, with incomprehensible accents and foggy plot). The subject bores me.

    Poetry, on the other hand, is a different matter.
    There is nothing surprising in the age of the poet – isn’t poetry by definition – the freshness of outlook, the grasping of underlying connections and associations of life expressed in concentrated poetic form – isn’t it all an extension of young and clear mind curious at the doorstep of incomprehensible world?
    All original poetry was written by young people. How old was Byron when he died? At what age Pushkin or Rimbaud written their best?

    I remember your very interesting post about Noor; it reminded of my own“>inquiries after reading it.

  6. The fact that Leo Marks’s parents owned the bookstore at 84 Charing Cross Road is a wonderful side piece of information.

  7. Tatyana…the original assignment of the coders at Grendon was simply the very mechanical operation of encrypting and decryping messages, using a key (the appropriate poem) which they had in their possession. The new assignment was to decrypt messages which had errors in them–apparently, the structure of the code was such that an error in a single character could make all of the subsequent message unreadable–which required more creative cryptographi skills.

    The way this potentially helped the Tennyson-loving agent was by reducing the odds that he would be required to retransmit a message. It didn’t always work–even with a greaty expanded group of well-trained FANYs, not all “indecipherables” could be broken.

  8. David, thanks. I understood the premise – but couldn’t find an explanation how exactly Marks solved this predicament. Maybe it’s expanded on in the book.

  9. @ Linc Wolverton

    Seriously? I love that movie – 84 Charing Cross Road – but haven’t read the book on which it’s based. Anyone around here who has? David Foster, I’m betting you have!

    – Madhu

Comments are closed.