Erna Skinner Was Mistress to Atom Spy Klaus Fuchs while Her Husband Ran Harwell

By Eleanor Voss · August 19, 2026

A marriage survived the secret liaison between the wife of a senior nuclear official and a Soviet agent, though the Security Service tracked the entanglement for years.

Erna Skinner slept with a man who was stealing the secrets of the atomic bomb from her husband's workplace. This intimacy existed within a tight social circle of physicists where professional trust and personal betrayal were indistinguishable.

According to a catalogue entry from The National Archives in the United Kingdom (KV 2/2081), the relationship was not merely a social acquaintance. The file's catalogue description records that Erna Skinner, described as Austrian/British, was the mistress of Klaus Fuchs. At the time, her husband, Professor Herbert Wakefield Banks Skinner, occupied a position of immense trust and authority in the British nuclear program.

Erna and the Atom Spy

The intimacy between Erna Skinner and Klaus Fuchs provides a human window into the vulnerabilities of the early atomic age. While the records do not detail the dates of the affair, they place it within a network of "close friends" that included some of the most important scientists in the West. The catalogue entry explicitly notes that Professor Skinner and his wife were close friends of both Fuchs and Bruno Pontecorvo.

Fuchs is identified in related catalogue entries (KV 2/1270, KV 2/1246, KV 2/1253, KV 2/1252, and KV 2/1251) as "the atom spy." These records describe him as an anti-Nazi agitator and a Communist who fled Germany for the UK in 1933. His trajectory took him through studies in Bristol and Edinburgh and research in Birmingham before he joined the British team tasked with the development of the atomic bomb.

For Erna Skinner, the risk was not merely social. For Fuchs, the relationship offered a potential bridge to the domestic life of a man who held the keys to the laboratory. In the world of intelligence, a mistress is rarely just a companion; she is a point of leverage or a source of inadvertent leakage.

Harwell's Deputy Director

Professor Herbert Wakefield Banks Skinner was not a peripheral figure. The catalogue description for KV 2/2081 records that he served as the Deputy Director of Harwell, reporting to Sir John Cockcroft. In this capacity, Skinner was the direct superior of both Klaus Fuchs and Bruno Pontecorvo.

The professional hierarchy was clear: Skinner gave the orders, and Fuchs carried them out. Simultaneously, Fuchs was engaged in a clandestine relationship with Skinner's wife. This created a paradox of authority. Skinner was responsible for the security and management of men who were, in one case, active Soviet agents and, in another, a man who would later defect to the Soviet Union.

Public records provide further weight to Skinner's importance. He was a physicist of significant standing who worked on radar at the Telecommunications Research Establishment and contributed to the Manhattan Project at the Berkeley Radiation Laboratory in the United States. His movements between the highest levels of British and American research made him a central node in the Allied nuclear effort.

"Nothing Significantly Adverse"

Despite the compromise of the Skinner household and the presence of a Soviet spy in his immediate social and professional orbit, the Security Service conducted an enquiry into the matter. The conclusion, as summarized in the catalogue entry for KV 2/2081, is strikingly brief: "Investigation showed nothing significantly adverse in a security context.

This phrase is a standard piece of intelligence jargon, but here it carries a peculiar weight. It suggests that the Security Service did not believe Professor Skinner himself was a collaborator or that the affair had provided Fuchs with a channel of intelligence that bypassed official security protocols. It ignores the psychological reality of the situation—the blindness or the tolerance of a husband whose wife is involved with a subordinate spy—and focuses strictly on the "security context."

The record does not explain how this conclusion was reached or whether Erna Skinner was questioned about her motivations. It simply clears the Professor of professional negligence or treason, leaving the personal wreckage of the marriage and the betrayal of the state as a secondary concern.

Berkeley Radiation Laboratory

The reach of this circle extended across the Atlantic. Skinner's work at the Berkeley Radiation Laboratory placed him at the heart of the American effort to build the bomb, the same ecosystem where Fuchs also operated. The proximity of these individuals—working together in Bristol, then at Harwell, and intersecting in the US—created a dense web of trust that the Soviet Union exploited with surgical precision.

The catalogue entries for Fuchs (KV 2/1270 through KV 2/1251) underscore the scale of the penetration, but the entry for Professor Skinner (KV 2/2081) highlights the fragility of the human barriers designed to protect those secrets. The Security Service's files on the "Subjects of Security Service Enquiry" capture a moment where the personal lives of the scientific elite became a matter of national survival.

Whether the Security Service ever fully understood the depth of the entanglement between the Skinners and Fuchs remains unclear. The catalogue entry records the result of the investigation, but it does not record the evidence. It leaves open the question of what, exactly, the British government considered "significantly adverse" when the Deputy Director of Harwell was hosting a Soviet spy as a close friend and a lover to his wife.