Yes, yes, I saw the Templar cave story.
The Templar Shropshire Trap – Google Docs
The Templar Shropshire Trap
The short version about that supposed Templar cavern found in Shropshire? The true, hidden version? It was never dug out, or even adapted, by the Templars. It has nothing to do with the Templars at all. The Templar cavern was instead carefully constructed in 1965 AD or so by an esoteric conspiracy with no love for humanity, and an obsessive desire to transform the world into something more to that conspiracy’s liking.
The background comes right out of GURPS Horror: The Madness Dossier: this reality that we live in right now (‘History A’) was created in 535 AD as the culmination of a rebellion of humans against their alien Anunnakku masters. The previous reality (‘History B’) was buried in a semantic and metaphysical ‘reality quake’ that wiped out an entire world, and put a new one in its place. But there were refugees from History B (‘irruptors’); and they struggle even today to put back the old world and bury our own. And, again: they have no love for humanity.
The Templar Shropshire temple-cavern did not exist in History B, exactly. But something like that would have existed eventually, if History A had not intervened; and so the irruptors and their human cultist servants are actively attempting to warp reality to the point where more and more things like the Templar caves have suddenly always existed. The more sites are retro-created, the easier it gets to insert them — so if the irruptors can get enough of these retro-historical sites up and running, History A’s grasp on reality will become steadily weaker and weaker.
At least, that’s the theory. Whether that theory can stand up to a carefully-constructed alternative explanation that can firmly weave the existence of sites like the Templar caves into the background of History A instead of History B is another story. Of course, if that doesn’t work then a satchel of C-4 would. Or at least plausibly might. No Templar cavern, no problem, right?