His wife, known as S, previously told the inquiry she agreed to his undercover work, but had no idea about his sexual relationship with another woman as he returned home five days a week.
The inquiry heard how she was led to believe he was “infiltrating terrorists”, and how she felt she should support his work.
Responding, Mr Jenner told the inquiry: “I thought financially we’d be secure and it would be a better future.
“It was a hell of a strain and on my mind all the time,” he said, adding: “I tried to blank it out.”
“The thought of deceiving her [his wife] above everybody else was an absolute abhorrence,” he said.
He told the inquiry he loved his wife but was a largely “absent father”, admitting “personal gratification and a police career took precedence”.
When asked why he continued to live with Alison for so many years, he told the inquiry it helped him “maintain his cover” and that it boosted his credibility among the people who he was spying on.