Alan Turing's mission to France, 1940

Alan Turing's mission to France, January 1940

Story from Enigma, Wladyslaw Kozaczuk (1979, 1984).

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The Polish book W kregu Enigmy, by Wladyslaw Kozaczuk, was published in Warsaw in 1979. The (American) English translation by Christopher Kasparek, Enigma, appeared in 1984. Kozaczuk gave a remarkable personal account of Alan Turing, as recalled by Marian Rejewski, the leading Polish cryptogist, in 1975. It appeared on page 97 of the English translation.

The setting was the farewell supper given before Turing's return to England, after he had spent several days with the exiled Polish cryptanalysts and the French hosts. From other sources, the date would appear to be in early January 1940.

For more on the context of this story, go to this page of the Alan Turing Internet Scrapbook.

In a cosy restaurant outside Paris staffed by Deuxième Bureau workers, the cryptologists and the chiefs of the secret decryptment center, Bertrand and Langer, wished to spend an evening in a casual atmosphere free of everyday concerns. Before the dishes ordered and the choice wine selected for the occasion had been served, the attention of the diners was drawn to a crystal flower glass with flowers, placed on the middle of the tablecloth. They were delicate rosy-lilac flowers with slender, funnel-shaped calyces. It was probably Langer who uttered their German and then their Polish names: "Herbstzeitlose ... Zimowity jesienne...."

This meant nothing to Turing, as he gazed in silence at the flowers and the dry lanceolate leaves. He was brought back from his reverie, however, by the Latin name, Colchicum autumnale (autumn crocus, or meadow saffron), spoken by mathematician-geographer Jerzy Rózycki.

"Why, that's a powerful poison!" said Turing in a raised voice.

To which Rózycki slowly, as though weighing each word, added: "It would suffice to bite into and suck at a couple of stalks in order to attain eternity."

Colchicum autumnale

For a moment there was an awkward silence. Soon, however, the crocuses and the treacherous beauty if the autumnal flowers were forgotten, and an animated discussion began at the richly laid table. But despite the earnest intention of the participants not to raise professional questions, it proved impossible to get completely away from Enigma. Once again, there was talk of the errors committed by German operators and of the perforated sheets, now machine- rather than handmade, which the British sent in series from Bletchley to the Poles working at Gretz-Armainvillers, outside Paris. The inventor of the perforated sheets, Zygalski, wondered why their measurements were so peculiar, with each little square being about eight and a half millimeters on a side.

"That's perfectly obvious," laughed Alan Turing. "It's simply one-third of an inch!"

This remark in turn gave rise to a dispute as to which system of measures and currency, the traditionally chaotic British one or the lucid decimal system used in France and Poland, could be regarded as the more logical and convenient. Turing jocularly and eloquently defended the former. What other currency in the world was as admirably divided as the pound sterling, composed of 240 pence (20 shillings, each containing 12 pence)? It alone enabled three, four, five, six or eight persons to prceisely, to the penny, split a tab (with tip, generally rounded off to a full pound) at a restaurant or pub.

The main point of this liaison meeting was documented on page 952 of the third volume of the official British Intelligence in the Second World War, F. H. Hinsley et al. (1988). At that stage the British had successfully mechanised the production of Zygalski's sheets for all 60 possible rotor choices. These could be used to attack the German Air Force signals which continued to use the simple indicator system that had allowed Polish pre-war penetration. But their use of the sheets was impeded by the fact that the turnover notches on rotors IV and V of the Enigma had been interchanged. It appears that this difficulty was resolved by the liaison meeting, so that GAF Enigma was broken by both British and Polish groups thereafter, using this method. After 1 May 1940, however, the situation was completely changed — first by the GAF abandoning this indicator system, and then by the fall of France.

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