In 1066, William upgraded his title from Bastard to Conqueror, concluding the demonstration to the English and the French that no matter their petty rivalries, Vikings are still better. (Or something like that.)
It occurs to me that the Order of Hermes would not have been entirely happy about being bystanders. The magi in the Stonehenge tribunal basically lost the mundane legal claim to all the land they owned. There may well be a grudge going both ways across the English Channel, based on what was negotiated with regard to how much the Hermetics could interfere with the war. Magi with a past in the Normandy Tribunal might even be forbidden to join the Stonehenge Tribunal, by long-standing custom(ie, everyone downvotes their presence at Tribunal).
But it's also been just over a hundred and fifty years since then. How would this disruption have influenced the Stonehenge magi?
Forgive me for the seeming Harry Potter parallelism, but it seems to me like the Order would have needed to largely withdraw and hide from the Norman occupation. I can see five major approaches:
#1: Suborn the new noble owner of the land. Meaning you'd better keep Willy(or his dynasty) from noticing that one of his valued subordinates is acting strange.
#2: Monastic camouflage. If noble women can create nunneries-in-name-only, so can magi. Invites both Infernal and Dominion interference. (Even Divine interference, sometimes.)
#3: Ex Misc ward experts. Set up places where mundanes can't easily intrude on, make it impossible to know there's even a Covenant there. Requires either a ton of effort or original research into something like wardstones that anchor an effect over an entire boundary. Isolates the Covenant, making it easier to slip towards Winter and ruin.
#4: Retreat into regios. Use one of the previous strategies, but either with a lighter touch or with an extra level of security.
#5: Diaspora. There may be a good reason everyone in Hibernia calls foreign magi "english". That's mostly who's shown up in the last 150 years.
Anyway, if substantial numbers of magi retreat into regios, that has the effect of making botches much more likely. Which moves Stonehenge magi that much closer to Twilight. However, it could also encourage them to develop the Virtues of Cautious Sorcerer and Flawless Magic. If those are then taught to the rising generations of magi, it could become a very common package, and that would tend to have the effect of reducing total Twilight exposure. And that means that Stonehenge could very well have an unusually large concentration of magi over 150 years old, with substantial lists of highly-mastered spells. Depending on how isolationist they are, they might not even bother to register as archmagi with the Order at large.
-Albert