The uncontroversial parts can be summed up easily enough, though. The O9A was probably founded sometime between 1960-1980 in Wales, with the most likely time-frame being the 1970s. The cult itself claims an origin, at least in its modern form, in the 1960s, and it emerged into the public eye as an already somewhat established group in the early 1980s. Its earliest known leader whose existence can be established reasonably well was a man called Anton Long, although since this was a pseudonym, some researchers have speculated that he could have been a small group of people based on differences in writing style between articles. More commonly, though, Long is believed to have been a single person, probably Tanzanian-born British citizen David Myatt, a man who was the apotheosis of all pasty white edgelords. At one point in the 1990s, he left Neo-Nazi Satanism only to convert to Islamic Jihadism, then just kind of abandoned that ideology in 2010. It's kind of funny seeing him LARP as an al-Qaeda military, right up until you realize that he probably founded a genuine terrorist group before growing out his beard and putting on a funny hat.
It isn't known for certain if the O9A emerged out of pre-existing esoteric sects. Some scholarly articles on the topic
do take their claim to have formed from three older groups seriously, although not their more elaborate mythos about those groups being pre-Christian survivals. There's just no believable documentation of organized pagan groups in the Welsh Marches from the Norman Conquest to the 20th century to back that up, and their beliefs have more in common with Crowley's ideas than anything from ancient Celtic mythology, regardless (although there is no particular reason to believe that they have any direct ties to any organization founded by Crowley himself or his close personal followers; esotericists in general like to mix and match ideas from different people, and while the O9A is distinctive for its Nazi shit and propensity to violence, it's no exception to that rule).
This article follows the most common narrative for the O9A's founding, although it seems a little too certain that Myatt was Anton Long.
This one, on the other hand, takes the O9A's claims to have been established from three older groups more seriously and remains noncommittal on Long's identity.
