Pocketsaviour - thanks for your reply. Can I ask how you got from outright denial to admission - was that in the same conversation or did you have to confront him again?
Things were very confused and he went back and forth. Initially I believed he had denied everything, however things that my mum said later made me think that he had admitted it to her. At the time I disclosed we were referred for a "family counselling session" via social services which was basically 60 minutes of him denying everything, talking about how isolated and lonely he felt, and making up reasons why I would have accused him (Childline, no new computer, etc.) It was an horrific experience. I did not speak.
(After I disclosed, I never spoke to him again. Silence was the only control I had, and I used it to the full. Ironic, since he had frequently controlled us by silent treatment. It's 28 years now since I last spoke to him.)
After I gave my statement to police, they told me that they would now interview him. If he denied events, they would definitely prosecute. If he admitted them, they would then make a decision to prosecute or not, or proceed with either NFA, a prosecution, or a caution. He was not prosecuted, so he must have admitted it. However I never received any official information from the police - that was all given to my mum, who changed the narrative to suit herself.
He wrote my mum a letter about a year after when he said he'd had to turn to me because she was frigid.
He was a very practised liar - he'd had a string of affairs throughout the marriage and somehow always made my mum fall for his lies. He was also a serial insurance fraudster. He would go back and forth with the lies and was always very convincing. He could make you doubt the evidence of your own eyes.