Back in London, Jean Claude was granted a short leave that was notable only for a pair of small disappointments. He and a friend picked up two women in a pub, but as they were heading home together the friend passed out from drinking too much gin and orange, and Jean Claude had to look after him and call it a night. Another evening Jean Claude and an Italian American OSS man decided to splurge on dinner at Frascati’s, a posh restaurant with a gorgeous marble grill room. They ordered lamb chops and were served mutton that tasted like soap.
After just a few days Jean Claude was taken to Thame Park, a grand estate in Oxfordshire where SOE ran its wireless school. The routine there was positively genteel—a far cry from Arisaig. Jean Claude was awakened each morning by a batman, a military servant, bearing a cup of tea. He would dress and go down to breakfast, spend the morning in classes, and have a long break for lunch. In the afternoon there were more classes, followed by a sort of high tea that served as dinner; Jean Claude relished slices of toast fried in bacon fat. The only drawback was the unremitting chill. There were radiators and fireplaces, but they were no match for the stone Tudor mansion’s cavernous spaces. The students frequently spent evenings in a warm village pub a mile away.
SOE wireless operators were nicknamed “pianists.” The first order of business was to get their Morse speed up to twenty-five words a minute, both transmitting and receiving. Once they reached that threshold they were introduced to the set they would be using, a Type 3 Mark II radio. Housed in a small suitcase, it had three main parts: a power supply that could work on a variety of DC and AC voltages, a highly sensitive receiver, and a transmitter whose frequencies were determined by crystals. It was a little heavy to pass for an ordinary suitcase full of personal effects, but it had a range of some five hundred miles.
Jean Claude’s Morse training at Area C had been in a closed, static-free system; now, for the first time, he was transmitting and receiving over the air. He was taught to tune his set as quickly as possible, and to limit transmissions to five minutes on any one frequency, to minimize the danger of detection by German direction finding.
Next came the all-important subject of coding and decoding messages. SOE had used several different encryption systems since the war began—including poem codes—and had discarded most of them as insecure or cumbersome. The notorious double transposition system, for instance, required that each message have a minimum of one hundred characters; that two numerical keys be used, each a different length; and that seven to ten dummy characters be added to the message so that the total number of its characters was divisible by five.1 Asking agents to use such a code in the field, in haste, often in conditions of terrible stress, was not sound practice.
Mercifully, by the time Jean Claude had his piano lessons, the brilliant Leo Marks had persuaded SOE’s spymasters to adopt a coding method that was at once simple to use and mathematically unbreakable. It was called the one-time pad, and it worked this way:
The agent in the field, and his handlers at the home station in London, had identical alphabetic tables for coding and decoding. The agent’s table was printed on a silk square, like a handkerchief. Here is a photo of the table Jean Claude carried:
A standard alphabet ran left to right along the top. Underneath each letter was an alphabet running vertically, and, in lowercase type next to it, a randomly scrambled alphabet, also running vertically.
The agent in the field carried a small pad with pages of keys: five-letter groups of random letters. The home station had an identical pad. Each line of random letters would be used once, snipped off, and discarded—hence the name one-time pad. Here is a photo of a page from a pad that was issued to Jean Claude:
To encode a message, an agent used the pad and the table together. Let us say the agent wanted to transmit the message:
s e n d g r e n a d e s
He would write that out, and then he would turn to his one-time pad. Starting at the top left, he would write the letters from the first line of the one-time pad above the plaintext. If he used the pad in the photo above, he would get this:
Y Y I N K R X I B W E Y
s e n d g r e n a d e s
Then, turning to his silk table, he would start with the key letter Y, go down that column to the letter s—the first letter in “send”—find that the code letter was q, and write it down. For the next letter in the message he would take the key letter Y, go down that column to the letter e, and find that the code letter was v. And so on. The result would look like this:
Y Y I N K R X I B W E Y
s e n d g r e n a d e s
q v t u p k d t e g n q
The agent would take the last, encoded line—q v t u p k d t e g n q— and send it by Morse code to the home station. The home station, using the identical key letters from a duplicate pad, would reverse the procedure to decode the message. Once the agent cut the top line of letters off the pad and destroyed it, the code could not be broken, even if an enemy got hold of the alphabet table.
The table was printed on silk so that if an agent was frisked, there would be no telltale crackle of paper. The pads were paper, printed with type so tiny it had to be read with a magnifying glass. Jean Claude carried his pads in a hidden compartment sewn into his wallet. Cut-away lines of key letters were supposed to be burned; Jean Claude found it simpler to eat them.
Each wireless operator was given his own security check to insert into messages, to confirm their authenticity. This usually took the form of a deliberate spelling error, such as replacing every tenth letter with the letter preceding it in the alphabet.
Jean Claude’s orderly mind was well suited to this kind of work, and he excelled at it—so much so that the trainers at Thame Park didn’t bother with his final exam. Jean Claude had been given to understand that the last exercise for pianists was a field test: They were expected to go to some English city with a wireless set, get a room, and meet a schedule of coded transmissions without being detected. But once again, SOE accelerated Jean Claude’s instruction. Skipping the field test, he was whisked from Thame Park to the RAF air base at Ringway, near Manchester, for parachute training.
The decision to abbreviate Jean Claude’s wireless training may have been necessary, but it substantially increased the risks to him and to fellow agents. At that very moment, SOE was suffering the deadliest setback in its short, eventful history, due to a lapse in wireless protocol.
The Germans called it Das Englandspiel, or the Game Against England. It began in March 1942, when an SOE wireless operator, H. M. G. Lauwers, was captured in the Netherlands by the Abwehr, the German military intelligence service. The Germans compelled him to send messages of their own devising to Baker Street. Lauwers omitted his security checks—he was supposed to garble every sixteenth letter—which should have alerted London that he was transmitting under duress. But somehow SOE’s N Section, which ran operations in the Netherlands, missed the signal.
A German counterintelligence team, led by Major Hermann Giskes, exploited this opening for the next two years. The Germans sent coded messages to N Section requesting parachute drops of arms, agents, and additional wireless sets. Agents were arrested the minute their feet touched the ground, and thoroughly interrogated. Giskes eventually had fourteen SOE wireless sets exchanging messages with Baker Street. His penetration of N Section was so thorough that he knew which brands of cigarettes SOE instructors preferred. He sent daily reports to Hitler.
Leo Marks smelled a rat. He noted that the messages arriving from the Netherlands were immaculately coded, without the (actual) errors that could be expected from field agents operating in stressful conditions, and suspected that they were the work of enemy cryptographers. He devised a little trap. He knew that German wireless operators customarily signed off their transmissions with the letters HH, for Heil Hitler. He had one of his cryptographers send a message to the Netherlands and end it with HH. In an instant, as if by reflex, came the reply—HH.
Even so, Marks was unable to persuade his superiors that N Section was blown. It wasn’t until two captured agents escaped from the Netherlands and sent an alarm from Switzerland that the ruse was detected. By then sixty-one Dutch and British agents had fallen into German hands; nearly all were shot.
Giskes wrapped up the Englandspiel with a message sent to Baker Street, in plaintext, on April Fool’s Day 1944. It read:
You are trying to make business in Netherlands without our assistance. We think this rather unfair in view of our long and successful cooperation as your sole agent. But never mind whenever you will come to pay a visit to the Continent you may be assured that you will be received with the same care and result as all those who you sent us before. So long.