Klaus Fuchs’s fifteen years in Britain had taken many paths, but it took Arthur Martin of MI5, sitting in downtown London in Leconfield House, only a couple of days to scour them in his security file. Now it was time for him to determine if the compilation of rumors and innuendos confirmed that this respected scientist was indeed Rest, the man who had shared the atomic secrets with Soviet Russia.
He composed a note, “Comparison of evidence from source with facts known of Klaus FUCHS,” to evaluate how well Fuchs’s personal history fit the evidence drawn from Venona, the top secret decoding project run by the U.S. Army Signal Intelligence Service:
Male?—yes
In US from March 1944 to July 1944?—yes, posted to Oak Ridge in August
Had contact with MSN report?—no document yet but probably British
Had a sister in US?—Probably
Details of the scientific project?—if project is atomic energy, they fit
Nationality?—yes, naturalized British
Assumption about transferring back to the UK?—fits but not conclusive
Movements of sister in October 1944?—fits if sister lives in Cambridge MA
Later that day, September 5, 1949, he melded his appraisal into a cable for the British embassy in Washington. It began by correcting the name of the individual in question—it was Klaus, not Karl. “Your para 1. Presume identical with Emil Julius Klaus Fuchs.” He then continued with Fuchs’s biographical data, stating that he had found a letter in Fuchs’s file from a Mrs. Klaus, signed Kristel, sent from Harvard University. He concluded, “Consider evidence against Fuchs very strong but not conclusive. All above information may be passed to the FBI with request for report on ‘Mrs. Klaus.’” He added that since Fuchs’s return from the United States, he was a senior researcher at Harwell, the Ministry of Supply’s main nuclear research center.
Martin sent this information to his boss, the director of B Branch, Dick White, with augmentation: summaries of what Martin labeled “adverse traces”—the incriminating information on Fuchs’s communist past.
1933—Landed UK. German Consulate Bristol inform Police that Fuchs was a member of the German Communist Party.
1940—Interned in UK and later Canada where he was reported to be very friendly with prominent Communist Hans Kahle.
1943—Source Kaspar reported that he belonged to the German Communist Party but, unlike his brother Gerhard, was never a prominent member. Gerhard Fuchs worked in the German Communist Party’s secret apparat.
There was good reason for Martin’s excluding “adverse traces” from the cable to the embassy: These facts were not for the eyes of the FBI. It put Fuchs’s security clearances in the spotlight, which might suggest grave lapses on the part of MI5. No need to tell all yet. Conclusions were still preliminary.
Just days into the investigation, a good part of Washington was searching for answers. The security staff at the British embassy, along with the FBI, was prying into every possible file to dig out the spy. All the while more code names tumbled out of the blocks of numbers in the Venona messages, Americans all. For the FBI, Fuchs was but one of many potential suspects in a Russian network.
The almost daily cables from both sides of the ocean threw out new leads, asked for follow-up, and occasionally closed a loop. They read with traditional British aplomb, inadequate to mask the urgency and tension that strained this case.
To narrow the odds on Fuchs, Martin needed a better understanding of the MSN report given to the Russians. For an expert with a high-level security clearance, the natural choice was Michael Perrin, a chemist by training and chief deputy at the Ministry of Supply in the atomic energy section with oversight for Harwell. It was an obvious role after his work coordinating the British bomb project before and during the war. He was fully conversant with Fuchs and the other members of the British mission. Besides that, people trusted his integrity and judgment. His father, an Episcopal bishop, had instilled modesty and an interest in others. He was easy to like, and people naturally turned to him.
Perrin’s name was familiar to Martin. He had just read the 1944 exchange in Fuchs’s security file between MI5 and Perrin on Fuchs’s stay in the United States. Perrin’s concern then, vis-à-vis Fuchs’s past, was not to “slip up in any way” with the Americans. MI5’s concern was to hide Fuchs’s possible communist “proclivities.” Now, five years after the fact, Perrin’s insights into the murky Venona messages might reveal whether his concern was merited. Martin set up an appointment.
On September 6, an MI5 team of Martin, his counterpart in surveillance, James Robertson, and their boss at B Branch, Dick White, met with Perrin in room 448 at Shell Mex House. The blockish thirteen-story white Art Deco building was home to the Ministry of Supply and only a couple of miles from MI5’s location near Hyde Park Corner. Its war wounds from bombing still lingered, but the flow of the Thames, which it fronted, lent a sense of calm and stability.
White opened the meeting by disclosing the source of the information to Perrin, although the chief deputy probably knew through a back channel. White stressed that the top secret nature of the decryptions made it impossible to use them in court. He had two questions for Perrin: Could atomic energy be the project at issue in all these machinations, and could Fuchs be Rest, the man who shared the secrets?
Perrin looked at the fragmentary messages and recognized the paper as “Effect of Fluctuation in the Flow of Nitrogen,” part 3 of MSN-12, written by Klaus Fuchs and published on June 6 in New York. He advised that this, together with the term “diffusion method,” a process to produce enriched uranium to use in an atomic bomb, indicated almost certainly that the targeted project was atomic energy. The comments about British scientists returning to England to set up their own plant carried weight too. Perrin didn’t think the Americans knew of it, but Fuchs, given his specialty in diffusion, could have guessed about the request for his being transferred back to the U.K. Weighing negatively, Perrin explained that the clue in the Venona message on the U.S.-U.K. agreement on atomic energy and the 1941 Atlantic Charter was wrong. The agreement on atomic energy had been signed by Churchill and Roosevelt later, at the Quebec Conference, in 1943.
As for Fuchs’s being Rest, Perrin considered it possible. The man’s general movements fit those in the messages. Important, though, was that Fuchs had not gone to Oak Ridge to work on diffusion. In this the FBI was wrong. Fuchs had gone to Los Alamos to work on the atomic bomb.
White, Robertson, and Martin left with the understanding that Perrin would follow up on loose threads: the MSN-12 paper; its circulation; Fuchs’s movements in the United States; and Fuchs’s family, especially his sister. The FBI, White emphasized, must be informed of all outcomes.
Martin’s partner, James Robertson, was an expert on surveillance, one of MI5’s best. He devised the where, when, and how of tracking a suspect, in this case with the hope of catching Fuchs’s handing over top secret documents. With a taboo on using the Venona source in court, and thus exposing the existence of that top secret decoding effort, MI5 needed concrete evidence of spying to prove its case.
Robertson and Martin were the lead team, the ground sleuth and the paper sleuth, men who were as different as their talents. Robertson was very much the British gentleman—the right schools and a master of the hunt, an especially appropriate status given that “Fuchs” was German for fox. He was the outside operational face to Martin’s inside interpreter of information.
Success for this very human hunt lay with a comprehensive surveillance web. The one that Robertson and Martin plotted that afternoon revolved around almost every minute of Fuchs’s day, every day. An inspection of all mail to and from his home and office; a phone tap in both places; around-the-clock physical surveillance when he left Harwell; a review of all bank records; and bugs in his home and office. Robertson had two choices for that—a microphone, conditional on the layout of Fuchs’s house, or something called an SF, a small washer placed in the phone that didn’t allow the connection to cut off. If he was spying, he had to pass documents to someone sometime, probably away from Harwell. They would watch twenty-four hours a day, and they would check every contact he made as well as documents he handled. Did he keep them longer than needed, did he take them outside Harwell, could they check for unidentified fingerprints? An effective surveillance net meant no holes.
MI5’s director general cautiously approved the plan. His uppermost worry: Fuchs must not sense eyes on him. Safety first, speed second.
Warrants for mail, phone, and bugging were the purview of the Home Office. Robertson prepared a one-page, single-spaced summary of the basic data on Fuchs’s life. He passed it through his boss, Dick White, and the director general. The basics were these:
Emil Julius Klaus Fuchs was born in Rüsselsheim, Germany, on December 29, 1911. He came to the U.K. in September 1933 to study physics at the University of Bristol and received a PhD in 1937. He moved to Edinburgh, Scotland, and received an ScD there in 1939. He was interned in Canada in 1940 after the war broke out and was sent back to the U.K. in January 1941. Later that year he moved to Birmingham to work with Professor Rudolf Peierls, where he began research on the atomic bomb. In 1943, when British scientists went to the United States to aid in research there, Fuchs was part of the team stationed in New York City. In 1944, he was transferred to Los Alamos. Throughout this period, MI5 examined his security record, mindful of the information from the German consulate in 1934, his friendship with Hans Kahle in the internment camp, and the informant Kaspar’s 1943 report on his communist leanings. The chief constables in Bristol, Edinburgh, and Birmingham, however, reported no problems. MI5 mail warrants in 1943 and 1947 had produced nothing. During the fortnight of surveillance in 1943, Fuchs didn’t receive even a single letter.
To justify the warrants to the Home Office, Robertson explained that a member of the British mission had passed information to the Soviets. Fuchs was under “considerable suspicion” partly because of previous communist views. With his key position at Harwell, he now required scrutiny. The warrants were granted.
The details in the summary were sound, but a discrepancy piqued Valentine Vivian, the deputy chief at MI5’s sister agency, MI6. Had Martin, he asked, “queried the Christian name or formed any ideas of your own as to how and why ‘Emil Julius Klaus Fuchs’ should have turned into ‘Karl’”? Martin didn’t know and suggested asking the security officers at the embassy in Washington to search their records because they had originally used that particular Christian name.
The instincts of the man from MI6 were astute, but his aim was askew. The real question was this: How did “Klaus Emil Julius Fuchs” transform into “Emil Julius Klaus Fuchs”?
The answer was that on September 24, 1933, when Fuchs crossed the channel and arrived at the port town of Folkestone, England, he was Klaus Emil Julius, as he had been for his entire twenty-one years. Within a month of his landing, a clerk accidentally transposed the Christian names on his official registration form. From that moment on, no matter the documents that he signed as “Klaus E. J. Fuchs,” he was officially Emil Fuchs (his father’s name) because his official registration card stated so. It took MI5 seventeen years to make the adjustment. The FBI never did.
Perrin had answers for Martin and Robertson the next day when the three met at Shell Mex House. A search through the records had reminded Perrin of details for the British mission’s assignment in the United States. To carry out the U.K.’s agreement on atomic energy made at the Quebec Conference in 1943, British experts on diffusion arrived in New York City at the end of that year. Only four remained there after March 1944. These were Fuchs, Rudi Peierls, Tony Skyrme, and Frank Kearton. All four had received a copy of MSN-12, as had six Americans in the Manhattan office. Staff sent the rest of the copies back to the U.K.
Perrin outlined the movements of these four from March through July 1944. Their movements matched those mentioned in the Venona messages, although Peierls more loosely than the other three. Martin had already learned that Peierls’s was the other name intelligence officers in Washington had proposed for “Rest,” simultaneously with Fuchs’s a few weeks before. A German émigré, Peierls had hired Fuchs to work with him in Birmingham in 1941.
Martin duly recorded Perrin’s frank opinions on the two new names. Of Skyrme, he wrote,
A young mathematician probably not more than 32 now. A “queer bird.” Wore his hair long and had an odd taste in clothes. Was always getting into scrapes. Celebrated his arrival in New York by getting arrested for some minor offence and spending his first night in a cell. An old Etonian. Believed to have gone to Cambridge on his return from U.S. and certainly not engaged in government work now.
Of Kearton, he wrote a more sympathetic description,
His duties were purely liaison. He would not have been considered for transfer to the U.K. to work on Diffusion. He was now a senior scientist at COURTLAULDS living in Foleshill Road in Coventry. He is British and, in Mr. Perrin’s view, it is practically inconceivable that he could be disloyal.
Martin sent Washington a long cable summarizing Perrin’s information. Washington replied with its own revelations. It was almost definite that Kristel Fuchs was Mrs. Robert Bloch Heinemann, who lived in Cambridge, Massachusetts. (MI5 was ignorant of her becoming “Christel.”) Meanwhile, information dug up by the FBI on the other three physicists as the FBI searched for any possible sisters streamed in to Martin.
Robertson’s surveillance plan included two personnel requests. Both focused on Harwell. One was the MI5 operative William James “Jim” Skardon, who would concentrate on surveillance at Harwell: mail, phone, and visual observation. The other was Wing Commander Henry Arnold, chief of security there. Arnold was a perfect source through his current position and his past experiences. As a wing commander during the war, he had worked on a secret project with scientists to destroy Nazi dams.
Robertson had a long list of needs from Arnold: Fuchs’s movement patterns around Harwell and frequency of trips to London; his character, habits, and acquaintances; a full personal description; upcoming trips to London; handling of top secret documents at Harwell with the possibility to check for fingerprints; the layout of Fuchs’s house, including any photography equipment there.
Directly observing Fuchs at Harwell was almost impossible. With the facility carved out of the RAF’s airfield, the largely barren fields gave no cover. A chain-link fence topped with three strands of barbed wire protected the scientific community from intrusion; loose rolls of barbed wire surrounded that. Armed security guards, stationed at the four gates, closely controlled the people, cars, and trucks entering and leaving. Adjacent to the compound, just outside the fence, perfectly aligned rows of newly constructed aluminum prefabs created a residential area. Any effort to observe someone’s movements would be quickly detected. Robertson needed the help of Henry Arnold at Harwell. It could be done fairly easily. Arnold and Fuchs already knew each other well.
In his early sixties, Arnold was dapper and handsome, friendly and entertaining. An amateur actor, a “superb” mimic, and a cellist, he could easily entertain with a well-told story. Equally evident were his talents as a sympathetic listener, which Arnold coupled with gentle and kindly advice. He encouraged those who sought his counsel, “Spit it all out in Uncle’s hand”—him being Uncle of course.
Arnold had a philosophy of security that meshed with his avuncular nature. To the scientists, including Fuchs, he explained that it was
[his] policy to carry out security in a spirit of trust, friendship and understanding of each individual, and that without such a basis on which to build, physical security controls could never operate successfully.
But beneath Arnold’s exterior as a talented raconteur, sympathetic listener, and kindly adviser, there was the dedicated professional who studied Hegel, Engels, and Marx to understand the loyalties of the believers. His warmth also hid certain prejudices:
By far the most important part of my work was to counter, by every means in my power and by personal influence, the foregoing beliefs which might exist in the minds of those employed at Harwell and whom I had selected for study.
That is, seeing himself adept at psychological profiling, he watched carefully for those who stood out as different, such as growing up in another country and being influenced by different “moral and political standards,” communism being a primary one. A tinge of anti-Semitism was there too, if not directly with Arnold, then in his office. Someone at Harwell thought Fuchs was Jewish and printed that word in the margin on a typed Harwell employment form.
Arnold intentionally suggested unusual security precautions to watch for reactions out of the norm. He once asked the scientists to leave the key to their safe with him when they were away. Most scoffed or laughed, but Fuchs, Arnold noted, willingly agreed.
Fuchs was just the kind of person to grab Arnold’s attention, as he said, one of those “people of alien origin,” a prejudicial attitude hardly peculiar to Arnold in that day.
The relationship between Arnold and Fuchs—one that had a hand in shaping history—began from their first days at Harwell. Within a couple of months of their both arriving at Harwell, in 1946, Arnold invited Fuchs to his house for coffee and after-dinner drinks. Before Fuchs arrived, another couple whom Arnold hardly knew but who lived in the Staff Club, as did Fuchs then, knocked on the door to bring him a gift of some special cheese. He invited them in; Fuchs came a little later; and they all chatted. Arnold assumed that Fuchs had engineered their visit because he didn’t want to be alone with him and his wife.
The episode was awkward, and Arnold didn’t wish to repeat it. “In the early days,” he later related, “[Fuchs] was a strangely silent person who seldom uttered, except when a question was put to him and then, if possible, he answered in a monosyllable.” Not a comfortable dinner guest, but someone Arnold wanted to befriend. He tried a different tack.
Arnold lived three doors away from the Bunemans and throughout the next few years dropped in, knowing that Fuchs also came by frequently for a drink. With Arnold’s being a bit leery of naturalized citizens, drinks and dinners at the Bunemans’ allowed him to keep an eye on two of them, Klaus and Oscar, plus Derek Behrens, who had associated with communists at Cambridge. What Arnold might have missed was that in keeping with the fickle enthusiasms of youth, and the swirling political currents of the times, Derek’s interest in communism arose mainly because, at their meetings, the communists had the best sandwiches.
Arnold wasn’t the only observer. Even with the conviviality, Mary noted a “distinct” reserve between Oscar and Klaus. It seemed at first that Oscar avoided getting too close socially. Even though neither was comfortable, she eventually realized that it was Klaus who created the distance. He dodged talking to Oscar alone except with regard to the Theoretical Division. To her, it didn’t make any sense.
Mary knew that the government’s 1940 policy of internment had caught up Oscar and Klaus—along with the thirty thousand other “enemy aliens.” She knew that the government had shipped both of them to internment camps in Canada. She knew that to keep away from Nazis in the camps, Oscar had requested to go to a “Kosher camp,” even though he wasn’t Jewish. She didn’t know that they sailed on the same ship to the same camp—or that it was Klaus who had finagled Oscar and other political refugees onto the kosher camp roster.
At Harwell, Klaus reported his former Social Democratic affiliation in Germany on government forms. Oscar Buneman knew the hidden side of Fuchs’s life. Mary had no inkling, but it seems that Henry Arnold did.
Around the time that Arnold invited Fuchs to his house in 1946, he contacted MI5. His initial memo didn’t indicate any misgivings, but it did set off an unexpected chain of events, all carefully delineated in Fuchs’s security file during the winter. Through it, Martin and Robertson learned that even back then Arnold didn’t consider Fuchs’s security record “above reproach.”
When Arnold arrived at Harwell in 1946, the scientists had a lax attitude toward security, and he quickly instituted discipline. One of his first requests to them was to inform him of their travel plans. As instructed, Fuchs wrote to Arnold to say that he would be in London on October 5, 1946, for a lecture of the Physics Club at the Royal Society.
Arnold forwarded Fuchs’s note to the MI5 official John Collard in London, asking if Collard wished to receive such information. A confused Collard responded that he wasn’t sure why Arnold had written: Did he question Fuchs’s integrity, or did he want to use Fuchs as an informant? In either case, Collard explained, he saw no need to act because Arnold had also talked to an MI5 official in field operations.
A few days later Collard had second thoughts, and he entered a note in Fuchs’s folder for the B Branch analyst Michael Serpell, one of the many who had reviewed Fuchs’s various clearances during the war. Collard suggested that Serpell contact the field operative about his conversation with Arnold. He also mentioned that Fuchs had just arrived back in the U.K. and was engaged in work at Harwell “of extreme importance.” This was news to Serpell.
Serpell spoke with the field operative whose information contained an unsettling sentence: “Arnold realizes from some quarter that FUCHS has or had a communist background.” This was the fall of 1946. Arnold had known Fuchs for only a couple of months, and he wasn’t privy to his security file. No one asked Arnold how he came by this tip.
The incident didn’t stop there. From previous security reviews, Serpell knew the Gestapo’s allegations against Fuchs. What alarmed him was his new position at Harwell. Serpell wrote a piercing summary of the risks associated with employing Fuchs in a top secret research facility:
The facts of this case seem to be that FUCHS in his youth acted as a communist penetration agent in the NSDAP. That he should have begun his political career in this undercover style seems to me to be of considerable significance at the present time. It is also apparent that as late as 1942 he was engaged in some communist activities in a refugee group at Birmingham. What does not seem to be conclusively established is that he was the Claus Fuchs mentioned as having been a close friend of Hans KAHLE in a Canadian internment camp. Although the subject of this file was interned, it was only for a short time (May 1940 to January 1941) and there does not seem to be any direct statement that his internment was in Canada. However, the identification is probable, and, if it is correct, the association with KAHLE may be regarded as particularly dangerous, since KAHLE is known to have acted as an OGPU representative in this country.
To Serpell, the probability that Kahle, a member of the Soviet secret police, the OGPU, would have recruited Fuchs was high.
He recognized that the British government didn’t see “the dangers inherent in the employment of such people as FUCHS” during the war, but with the war over he assumed that the danger to security would be a prime issue. Compelled by this broadside, the head of countersubversion in B Branch, Roger Hollis, finally requested verification that “Claus Fuchs” in internment and “Klaus Fuchs” at Harwell were the same person. The answer: they were.
With that answer, Hollis immediately disputed Serpell’s speculation on the Fuchs-Kahle relationship. He argued that the government had shipped many Nazis to Canada and mistakenly included a few anti-Nazis. For Fuchs and Kahle to become friends was hardly surprising, “surrounded as they must have been by Nazis who would have been uncongenial to them.”
Serpell’s memo also implicated Rudi Peierls at the University of Birmingham. Peierls consulted at Harwell, was friends with Fuchs, had a Russian wife, and visited Russia in 1937.
Serpell’s attack ruffled staff at MI5. Concerned only with security in the postwar era and not science, junior officers pushed to “divorce” Fuchs “from all contact with atomic energy” and no longer use Peierls as a consultant. The chiefs thought there was “nothing of a positive nature” against either of them. Minutes, charged with emotions, flew back and forth into early 1947.
Finally, on January 14, 1947, Hollis ordered warrants on the mail of Fuchs and Peierls. Clerks dutifully hand copied all letters sent to the two physicists for the next two months. A few with sealing wax went unopened. Nothing of importance to MI5 turned up.
Arnold never knew about the buzz in MI5 caused by his initial request to Collard.
With Arnold’s suspicions about Fuchs since 1946, Robertson didn’t need much context for briefing him on surveillance of Fuchs at Harwell. In their first meeting, he went right to the point: MI5 “had recently received information throwing suspicion upon one of a limited number of British scientists, the particular individual in question having not yet been identified. Fuchs was one of the number.” And he warned: Only a handful of people know about this. Tell no one else. Do not make any inquiries. Put little information on paper.
Arnold was able to supply ample background: Fuchs had just moved into a prefab at Harwell; he didn’t have a phone but would probably get one; he had an old Morris eight-horsepower motorcar; he traveled to Birmingham, sometimes to Oxford, London rarely, and usually by train; appropriate to his position he had many foreign visitors; and he had a few close friends at Harwell, particularly the Skinners. Herbert Skinner was his boss. Suspected of having TB, Fuchs had lived at the Skinners’ and still often slept there. In six months, the Skinners were moving to Liverpool, where Herbert would take up a physics chair at the university. Herbert divided his time between the two places. Fuchs, Arnold reported, “is on more than friendly terms with Mrs. Skinner.” He summed up:
[Fuchs] is a very reserved man, and mentally tough. Nevertheless, he is fond of both whiskey and women and can take a large amount of alcohol without being affected. He is a man who is not only brilliant intellectually, but also extremely shrewd from a practical point of view.
Arnold held his cards close, but he certainly signaled to MI5 his own wary attitude toward Fuchs.