Ursula Maria Kuczynski was second of the six recorded children born to the distinguished Economist and demographer Robert René Kuczynski and his wife Berta Gradenwitz/Kuczynski, who was a Painter. The children were academically gifted and the family was prosperous. Her elder brother, Jürgen would later become a distinguished historian-economist who had a controversial relationship of his own with the espionage community. Ursula grew up in a small villa in the Schlachtensee quarter in the southwest of Berlin. When she was eleven she landed a screen role in The House of Three Girls (1918), the cinema version of Das Dreimäderlhaus.

She attended the Lyzeum (secondary school) in Berlin-Zehlendorf and then, between 1924 and 1926, undertook an apprenticeship as a book dealer. She had already, in 1924, joined the left-leaning Free Employees league (AfA-Bund), and 1924 was also the year in which she joined the Young Communists (KJVD) and Germany's Red Aid (Rote Hilfe). In 1926, the year of her nineteenth birthday, Ursula Kuczynski joined the Communist Party of Germany.

In 1926/27 she attended a librarianship academy while working at a lending library. She then took a job at Ullstein Verlag, a large Berlin publishing house. However, she lost this job in 1928 after participating in a May-Day Demonstration and/or on account of her Communist Party membership. Between December 1928 and August 1929 she worked in a New York book shop before returning to Berlin where she married her first husband, Rudolf Hamburger, who was an Architect and fellow member of the Communist Party. It was also at this time that she set up the Marxist Workers' Library (MAB) in Berlin which she headed up between August 1929 and June 1930.

With her husband she relocated, in July 1930, to Shanghai where a frenetic construction boom afforded ample opportunities for Hamburger's architectural work. She would remain based in China till 1935. It was here that the couple's son, the Shakespeare scholar Maik Hamburger, was born in February 1931. After they had been in Shanghai for a little more than four months she was introduced by the US Journalist Agnes Smedley to another German expatriate, Richard Sorge, outwardly a Journalist, who is better remembered as "Ramsai" an active agent of the Soviet Intelligence Directorate (GRU). Sources are vague as to whether the Hamburgers were already working for the GRU before they left Germany for China, but in any case it was after the meeting with Sorge that between 1930 and 1935 "Sonja" (the cover name by which Kuczynski was known in The Service - means dormouse in Russian) operated a Russian spy ring under Sorge's direction.

In Autumn 1934 she had to send her son Michael to live with her husband's parents (now relocated from Germany to Czechoslovakia) when she was sent to Moscow where she undertook a seven-month training session before returning to China. There had been a concern that if baby Michael had accompanied her to Moscow he might inadvertently have blown her cover later by blurting out words in Russian. It was also during this period that she mastered various practical aspects of spy-craft. This included radio operator skills that were much prized in the world of espionage: she learned to build and operate a radio receiver, becoming an exceptionally fluent and accurate user of Morse code. Between March and December 1934 she was based in Shen Yang in Manchuria which had been under Japanese military occupation since 1931. Here she met the GRU's chief agent who was working under the name "Ernst". Sonja and Ernst had a romance which would result in the birth of her daughter Janina in April 1936. Her husband Rudolf Hamburger generously acknowledged "Nina" as though she were his own daughter. The GRU was nevertheless concerned that the affair with Ernst might lead to the unmasking of both agents, and she was recalled with Rudolf to Moscow in August 1935. In September 1935 they were both posted to Poland where, apart from at least one more lengthy visit to Moscow, they would remain till Autumn 1938. In the meantime it would later transpire that in 1937 the Soviets awarded her the Order of the Red Banner for her espionage work in China. Without ever wearing a uniform, she now held the rank of colonel in the Soviet military.

Between Autumn 1938 and December 1940, as agent "Sonja Schultz", she was based, still with her husband Rudolf Hamburger (de), in Switzerland where she was one of the so-called "red three", together with Sándor Radó: her duties included working as a specialist radio operator, applying technical skills acquired during her Moscow visits earlier in the decade. The codes she used to send information to Moscow from her little house in Caux, a three-hour walk up into the mountains above Montreux, have never been deciphered. In Switzerland, which was where her marriage with Rudolf Hamburger finally broke apart, she collaborated with the Lucy spy ring and was involved in recruiting agents to be infiltrated into Germany. After the Nazi take-over of Danzig in Autumn 1939 she also set up a resistance group in the formerly free city.

She divorced later that same year, and early in 1940, while still in Switzerland, married her second husband. Len Beurton, like her, was working for the Soviet GRU, and like Kuczynski he came with an unusually wide range of names. He also came with a British passport, and by marrying him Agent Sonya automatically acquired a British passport too. Sent by the GRU she and her new husband now relocated from Switzerland to England where she would remain for the rest of the 1940s, and where her second son was born in the late summer of 1943. They had settled in north Oxford, but soon moved on to the first of a succession of nearby villages, settling initially in Glympton, and then in Kidlington. In May 1945 the Beurtons relocated again, to a larger house in the north Oxfordshire village of Great Rollright where they remained till 1949 or 1950, becoming so integrated into the village community that both her parents, who were frequent visitors in Oxfordshire even after the war ended, and who both died in 1947, are buried in the Great Rollright churchyard. In each Oxfordshire property in which she lived Agent Sonya installed a radio receiver and transmitter (which during the war would have been considered illegal had it come to the attention of the authorities). Living in Oxfordshire placed them conveniently close to Ursula's parents who had emigrated to London after 1933, and were then living with friends in Oxford because of the air raids in London.

What is incontrovertible is that she engaged in an exceptionally high risk trade on behalf of Stalin's Intelligence machine without being shot by the enemy or sent to the Gulag by her own side. Her husband and the father of her first son, Rudolf Hamburger, who also worked for Soviet intelligence, fell foul of the Soviet regime in 1943 and was deported to the Gulag in the east of the Soviet Union. He was released in 1952 but remained officially "banned" and was sent to Ukraine, only being permitted to return to Germany in 1955. This type of experience was far from unusual among Soviet spies. Sandór Radó with whom she had worked so closely in the hills above Geneva also spent long years as a guest of the Russian Gulag. Richard Sorge, who probably recruited her to work for Moscow in the first place, was caught and hanged by the Japanese. Werner herself, as far as her story has come into the public domain, suffered nothing more harrowing than a couple of pointed but ultimately inconclusive meetings with British Intelligence agents in 1947, and was able to escape to the safe haven of East Germany before her espionage activities became the subject of any trial or other retributive process. Simple survival represented a considerable achievement under the circumstances of her two decades in espionage, and seem to justify the media epithets she attracted to the effect that she was "Stalin's best spy" ("Stalins beste Spionin").

The Beurtons' Oxfordshire village homes were also close to the UK's Atomic Research Centre at Harwell, and to Blenheim Palace, where a large part of the British intelligence Service had been relocated at the start of the war. In Oxfordshire, together with Erich Henschke, she worked on infiltrating German Communist exiles into the US Intelligence Agency. By Autumn 1944 she and Henschke had succeeded in penetrating UK activities of the US Intelligence Service (OSS). The Americans were at this time preparing an effort called "Operation Hammer" for parachuting UK-based German exiles into Germany. Ursula Beurton was able to ensure that a substantial number of the parachuted OSS agents would be reliable communists, able and willing to make inside intelligence from the "Third Reich" available not merely to the US military in Washington, but also to Moscow.

Many years later Ruth Werner (as she would by that time have become known) recalled that she was twice visited by MI5 representatives in 1947, and asked about her links with Soviet intelligence, which Werner refused to discuss. Werner's communist sympathies were no secret, but it seems that British suspicions were insufficiently supported by evidence to justify her arrest. Her visitors were unaware of or unconcerned by her periodic, and apparently Casual, meetings with Fuchs in Banbury or on country cycle rides. At that time the British intelligence services seem to have been disinclined to follow up their concerns. Two years later detonation of the first Soviet atomic bomb refocused priorities within MI5, however. Klaus Fuchs was arrested towards the end of 1949; in January 1950 he was put on trial and confessed that he was a spy. The day before his trial started, fearing that she was about to be unmasked, Agent Sonya left England. In March 1950, after two decades away from the city of her birth, she turned up back in Berlin. Meanwhile, Klaus Fuchs finally identified her as his Soviet contact in November 1950. The espionage-related aspects of her friendship with Melita Norwood only began to emerge several decades later.

Germany had changed. Ursula Beurton returned to East Berlin in the Soviet occupation zone of what remained of the country, although the Soviet Military Administration had by now retreated into the background following the formal establishment of the German Democratic Republic in October 1949. A systematic nation building process had actually been underway for several years before 1949, starting with the arrival from Moscow of 30 well prepared formerly exiled German communists in Berlin at the start of May 1945, led by a man called Walter Ulbricht. One change was the disappearance in the new country of the Communist Party of Germany. In fact, the party had not exactly disappeared, but it had been replaced in April 1946 through the contentious merger of the Communist party with the East German elements of the old German Social Democratic Party (SPD), to form the Socialist Unity Party of Germany (SED / Sozialistische Einheitspartei Deutschlands). On her arrival in East Berlin Beurton lost little time in resigning from the GRU and joining the SED. Six years later she started to re-emerge with a new life as an author. In the meantime, she undertook some journalism and other writing work. She was given a government job in 1950 as head of the Capitalist Countries Division in the Central Department of Foreign Information in the Government Information Office. She was later fired from the Government Information office, reportedly because she forgot properly to lock the armour plated door of a large safe. Between 1953 and 1956 she worked in the Chamber of Commerce for foreign trade.

She lived another ten years and seems never to have regretted or seen the need to apologize for her espionage. Back in 1956, when Nikita Khrushchev made public the darker face of Communist Russia under Stalin, she was invited to comment. She was reluctant to join the criticism of the Soviet wartime leader:

Between 1958 and 1988, she produced a succession of books under the name by which she subsequently came to be known, Ruth Werner. Most were story books for children or suitably expurgated memoirs of her time in espionage. Her autobiography appeared in East Germany under the title "Sonjas Rapport" (Sonya's Report) and became a bestseller. There was no mention of Klaus Fuchs who was still alive in 1976, and, presumably for the same reason, no mention of Melita Norwood. An English language version appeared in 1991 and a Chinese translation in 1999. An uncensored German language version came out only in 2006, although many questions were still left unanswered.

In 1982 Ruth Werner became a member of the East German affiliate of PEN International.

Since 1989 more information has become available concerning at least some of her espionage achievements, and appreciation of Ruth Werner's exceptional abilities has grown. In the opinion of one Historian who has studied her career, she was "one of the top spies ever produced by the Soviet Union and her penetration of Britain's secrets and MI5 possibly went far deeper than was thought at the time she was operational." An unidentified GRU chief is reported to have observed during the war, "If we had five Sonyas in England, the war would end sooner." Werner herself could be more reticent about her contribution: "I was simply working as a messenger" ("Ich arbeitete ja bloß als Kurier.")

Interviewed in 2000, a few months before her death, she was asked about the consequences of "Die Wende", the changes which had led to German reunification (which many of her persuasion still saw as a peaceful annexation of East Germany by West Germany):