Mr. Oakes did not respond to requests for comment. A spokesman for Cambridge Analytica endeavored to distance the company from Mr. Oakes and his comments, saying he “never had any role at Cambridge Analytica, has never worked for Cambridge Analytica and did not work on the Trump campaign in any way whatsoever.”

Image Nigel Oakes of SCL Group, the parent company of Cambridge Analytica.

The company said his comments were made “in a personal capacity about the historical use of propaganda to an academic he knew well from her work in the defense sphere.”

The hearings marked a sudden public exposure for Mr. Oakes, an upper-crust Englishman whose air of mystery was also a selling point. From its inception, the central promise of the SCL Group was to shape public opinion without being seen. Dr. Briant, who interviewed Mr. Oakes repeatedly for her book “Propaganda and Counter-Terrorism: Strategies for Global Change,” said she suspected that for Mr. Oakes, the hearings had been a painful experience.

“You need to bear in mind, these are powerful, arrogant men,” she said. “They think they own the world. I honestly think they thought they were invincible.”

As a young man, Mr. Oakes cut a rakish figure. Raised in rural gentility — his father was once the high sheriff of Warwickshire — and educated at Eton, he had “a kind of smoothness and charm and charisma that you associate with people who have that kind of education,” his former colleague Barrie Gunter said.

After Eton, instead of continuing on to college, he embarked on a racy career as a disc jockey and music producer and dated Lady Helen Windsor, a cousin of Queen Elizabeth and 40th in line to the throne.

The business idea he brought to the team of psychologists was “Marketing Aromatics,” a service that pumped in fragrances — of pine trees, the ocean, or new-mown grass — on the principle that “smells can influence attitudes and therefore behavior.” Mr. Oakes was “a young man in a hurry,” under pressure to repay his investors, said Professor Gunter, of the department of mass communications at the University of Leicester.