Cockney Steve,
Just a finer point, but the most detonation prone mixture is one that occurs around 35-50dF ROP. This happens after leaning past the best power point of 75dF ROP.
This is not to say that when conditions are right that you can't get mild detonation starting a bit earlier, because it depends on the severity of the conditions. These boundaries are very fuzzy ones but they do not extend past peak or if they do it is not easily perceivable as no LOP mixtures support detonation. One caveat here, perhaps some poor octane mogas in just the right conditions (read hard to achieve) will continue to detonate mildly at just LOP but not for long after that. Avgas at min spec or G100UL at min spec does not.
In the quest to provide the world with a certified unleaded Avgas with equal or better properties GAMI have been doing hundreds of hours of detonation testing on all manner of fuels, and I am privileged to be involved in a small way. The Data shows where common misbeliefs are simply that.
I am sure over the last 15 years Walter Atkinson has seen plenty more of this himself and would validate this.
Just to provide some balance here as many people get these two things mixed up, pre ignition events can occur while LOP, although most likely at higher powers so typically for that to happen it will need to be in a turbocharged engine.