Between Silk and Cyanide (27 page)

The FANYs once again proved me wrong, and the more adventurous of them now used the charts on all indecipherables and ostentatiously teleprinted at the foot of the messages 'broken on your chart system'. One young FANY, as bright as she was cheeky, had asked why I hadn't also calculated the last lines of messages because surely they would be just as useful as the first? I didn't tell her that there were two reasons. One that I hadn't thought of it, the other that it was extremely hard and time-consuming work. But she was right, of course, and Tiltman day was the ideal occasion for making a start. I reached for a mountain of squared paper, gritted my arithmetic and began the calculations.

Like all acts of minor expertise, it was wholly absorbing and some hours or weeks later I glanced up and found two men watching me from the doorway. One was Nick, the other was a large teddy bear of a colonel with amused eyes.

I'd seen those eyes before when they'd had nothing to amuse them. They'd aged a thousand ciphers since then.

The supremo had called at the code-breaking school in Bedford to interview candidates for Bletchley. Of the twenty-five pupils on the course, I was the only one not sent in to him for fear of wasting his time. But by standing on tiptoe and peering over the other pupils' shoulders I'd managed to gaze at him across the great divide called talent. That was ten months ago.

The divide seemed even greater as I shook his hand. I then shook Nick's for producing him.

Slightly puzzled by these SOE formalities, the supremo said that my face seemed familiar. I explained that we'd once been at opposite ends of the same corridor but didn't add how certain I was that we always would be.

There was a short pause as the two master signallers discussed a tual acquaintance who apparently had last been seen entering a public toilet and hadn't been heard of since. It sounded like shorthand joining C. Glancing at his watch. Nick reminded Tiltman that he I another appointment as soon as he'd finished with me. He then the room rapidly before I could shake his hand again.

I was alone with my coding godfather.

And Gambier-Parry.

Tiltman sat opposite me with the WOK at right angles to his navel, and wasted no time on preliminaries. Opening his briefcase, which had more locks on it than leather, he produced a document which I finally recognized as my coding report. He then read it from cover to cover while I did my best to remember what I'd written. Gazing for a moment into the middle distance—my middle, his distance—he then delivered his verdict like a magistrate anxious to proceed with his next case. He endorsed the report's view that the poem-code was unsuitable for SOE's traffic, and agreed that 'its security checks were valueless except as a means of giving agents confidence'.

There was nothing he wished to add to the list of security precautions already in use (most of them had come from him anyway).

The idea of giving agents original composition was sound, though he sympathized with those who preferred famous quotations which they already knew by heart. But he was puzzled by the report's reference to 'compromise poems'. Would I please explain what they were? I told him that some agents allowed me to alter a few words of their famous quotations, which I thought was better security than making no changes at all. He asked to see an example.

I produced one which I'd given to Peter Churchill to use as a reserve:

The boy stood on the burning deck
His feet were full of blisters
He hadn't got them from the fire
But from screwing both his sisters.

I didn't repeat Peter's comment that he hardly ever screwed with feet because he had ingrowing toe-nails but I couldn't resist adding that this agent's indecipherables were particularly tricky as regularly 'hatted' his columns. I wanted to establish that I knew the jargon.

Tiltman's eyes became sheets of calculus at the mention of indecipherables but he said that we'd come to those shortly.

Having established which of us was setting the pace of the meeting, he thoroughly endorsed the concept of giving agents a supply of poems on microfilm. But this brought him to another point which the report hadn't made clear.

His question seemed harmless enough at first hearing. When WT operators were at training school, did they transmit their practice mesages in the poems which they were going to use when they reached the field?

I said that I'd stopped them from doing this as trainee operators worked together in teams and could get to know each other's poems. Did he think I was right?

He nodded, and seemed relieved at my answer.

I was convinced that there was something behind his question which I hadn't spotted and registered it for a future brood.

He was silent for a moment and looked restlessly round the office as if wondering what he was doing here. His mind was clearly on other matters and I felt the weight in the room of some terrible responsibility.

Then the sheets of calculus returned and he was ready to talk about indecipherables.

He found that this part of the report was written for laymen and gave no indication of the techniques we used to break indecipherables. Nor did it explain how girls with no previous cipher experience and whose average age was twenty had been turned into a team of code-breakers. So would I cast my mind back to June '42, when SOE took over its traffic from C, and explain in detail what our techniques were, how the girls had been trained, and anything else that might be relevant to a subject which was new to him?

I dried up completely—not because I didn't want to discuss the only corner I could call my own but because by Bletchley's standards we had no techniques. The deep brown melter managed to provide a few statistics:

When I joined SOE in '42 approximately a quarter of all incoming messages were indecipherable due to careless coding or acute Morse mutilation. In July '42 I gave my first lecture on code-breaking, and in the following week the percentage of indecipherables broken by the Home Station rose from 3 per cent to 28 per cent, to 35 per cent the next week, then six weeks later to 62 per cent, then to 88 per cent, then rose to a peak of 92 per cent, and steadied itself at an average of 80 per cent: The number of indecipherables broken to date was 930, and the number of keys tried approximately 800,000. The sheets of calculus awaited the techniques.

Since the subject was new to him (or so he said) I reminded him that if a message hadn't been broken by the time an agent's next schedule was due, the certain knowledge that he'd be ordered to repeat it forced us to use rudimentary methods designed to beat the clock.

'Regard me as the clock,' he said. 'What are the methods?'

I described the 'blanket attacks' of 1,000 keys at a time undertaken by successive shifts of coders, the anagramming based on a message's probable contents and the agent's language patterns, the analysis of the agent's previous mistakes both in training and in the field, and the tests for 'hatted columns', misnumbered code-keys and Morse mutilation of the indicator-groups.

'How did you teach this to them? I'd like the details, please.'

I described my first visit to Grendon when I'd written a coded message on the blackboard and shown the girls how enemy cryptographers would break it. I told him how eagerly they'd joined in until clear-text emerged: 'THERE SHALL BE NO SUCH THING AS AN INDECIPHERABLE MESSAGE', which had become their motto. They'd then helped me to reconstruct the poem on which the message had been based: 'BE NEAR ME WHEN MY LIGHT IS LOW', which I thought about whenever I briefed agents. I then poured out all the reasons why we had to change the face of agents' coding, and described SOE's resistance to anything new until the miracle of Nicholls, which resulted in today, and many tummy rumbles later (mine) I realized that I'd delivered a lecture without any idea of how long I'd been speaking, and hoped it was still February.

He was silent for a full minute after I'd finished. The sheets of calculus had gone but I couldn't read what had taken their place and waited to be told to go back to Bedford for a refresher course.

Instead he quietly asked if the charts he'd seen me using when he and Nick arrived had any connection with breaking indecipherables. I confirmed that they had. He at once asked me to explain how they worked.

I forgot that I was talking to Tiltman and began explaining how to read off the first line of a message as if the cryptographic supremo were a Grendon coder. When I tried to change style he shook his head impatiently, so I continued my exposition in FANY language. Ie waited for me to finish, then demanded to know who had devised these charts.

'You, sir.'

He looked at me in astonishment.

Since surprised bears need careful handling I hastily explained that the charts were only an extension of a method we'd been taught at Bedford called 'reading the heads of columns'.

'An extension, you say? I see! And how long ago did you extend it?'

I told him that the charts had been in use for roughly three weeks.

It was my turn to be astonished when he said he'd like me to demonstrate the charts on an unbroken indecipherable. When I most needed an indecipherable, there wasn't one in the office, even from from the Free French! I wondered if he'd believe me.

bwas rescued by my red-haired typing pool, Muriel, who quietly brought with her Skinnarland's latest indecipherable which the day squad had been unable to budge. She knew his traffic had absolute priority and hoped the colonel would forgive the interruption. The colonel not only forgave with a subaltern's smile but accepted her offer of a cup of tea. It was Heffer who'd told me that red was a professional soldier's favourite colour.

I realized what a poor host I'd been. Tiltman hadn't broken a code in several hours and might be suffering from withdrawal symptoms. I invited him to help us with this urgent indecipherable and perhaps he'd like to try the charts for himself. Less than ten seconds later the thinking man's teddy bear was sitting beside me waiting to be briefed.

I gave him a break-down of one of our most regular customers' coding habits, warning him that the villain always started his messages with five dummy letters, the only security rule he never forgot. I then kitted him out with charts and squared paper, and even pushed the WOK on one side to give him more room. He asked me to suggest the best line of attack and I gave him the list of keys waiting to be tried. He began work at once, numbering his transposition-keys in less time than it took Tommy and me to light our cigars. Wishing I had a camera because I certainly wouldn't believe this tomorrow, and doubted if I would tonight, I watched him demolishing the keys with astonishing agility. It took me a little while to realize that there was something not quite right about the way he was doing it. Although he was executing the four mandatory movements—number transposition-key, consult chart, select the letters it indicates, see if they make sense—his speed was the equivalent of a one-minute mile, and there could be only one explanation for it: the Tiltman method was to number the transposition-key, glance cursorily at the charts,
and calculate in his head which letters would appear in the first line of the message
—an awesome achievement even for a cryptographic supremo. This suspicion was confirmed when I 'accidentally' handed him the wrong chart and he still produced the right set of letters.

He seemed suddenly to realize that this was becoming a spectator sport, and pointed out the list of keys. 'Can't manage all of 'em.'

I took over the bottom half of the list and hobbled along behind him.

Skinnarland continued to defy the pair of us like the champ that he was until I suddenly noticed that there was neither sound nor movement coming from my left. I glanced up and found that our newest recruit was holding a sheet of squared paper towards me as proudly as any FANY with her first success.

Skinnarland's first line read: 'TGOHL [dummy letters] THE GERMANS ARE INCREAS—'
[14]

I remembered that I wasn't supposed to let Tiltman see any of our traffic, nor could I read the clear-text to Wilson while he was still in the room. He seemed to be preoccupied with studying the charts, and I scrambled the right key to the Grendon supervisor, instructing her to teleprint the clear-text to London with absolute priority. I accepted congratulations guiltily.

Giving me no chance to thank him, Tiltman asked if he could have a set of charts to take back to Bletchley, and if I'd calculated the last lines he'd like those as well. I handed him a spare set, which disappeared at once into his jewel-box, and promised him the last lines an as they were ready.

He was still sitting companionably beside me and I made the novices mistake of basking in the moment. A sidesweep from the bear's paw took me completely off guard. 'Do you suspect that any agents lown and sending their messages under duress?'

Hoping to learn from his timing, I said that I stood by what I'd written in the report. No reliance could be placed on the poem-code's security checks as they were little more than a gesture to give the agents confidence, or on the poem-code itself, and there was nothing I could add to this.

'But what about irregularities in their coding or their WT transmissions? Are you saying there haven't been any?'

I had to stop myself from showing him the file of an agent called Kergolay whom even SOE realized was blown. He'd gone into France in 1941, and was the first WT operator to send London an indeciphrable.
[15]

He was a Skinnarland-class coder and an equally inept operator, but in mid-'42 he began transmitting on another circuit's set and his coding and WT craftsmanship were suddenly transformed. No indecipherables, little or no Morse mutilation, scarcely any procedural irregularities. The whole of Signals—including Ozanne—was convinced that he was caught and so was Buckmaster, who was still keeping up the pretence of exchanging messages with him in a brilliant attempt to prolong his life. This was a rare example of country section and Signals directorate working as one.