I'm not entirely sure what helped me overcome the problem. If I'm relaxed, my speech is fluent. If I take deep breaths and think about what I'm going to say, the stutter rarely shows up. There are, of course, some words that I mispronounce still like "manipulative".
The only real ongoing issue is the learned habit of speaking quickly to try and overcome the stutter. Internally, I can understand exactly what I said, but externally it apparently comes out as a stream of unintelligible words. That's something I'm still working on.
The stutter comes back when I'm tired, nervous, or stressed. Apart from that, it's barely noticeable which I am pleased about.
How curious to know that it's all in the brain rather than a psychological cause such as anxiety which is what my parents used to assume. Perhaps I shall have to volunteer to help with future research.