JF and others...
I've previously met (and sadly helped AAIB investigate) the phenomenon of very high lateral stability (Lv) at high AoA with a delta.
On another track, I recall that the Jaguar (which has a very low B:A, like Concorde) had a real problem with intertia coupling at high AoA causing a divergent roll:yaw oscillation (not a spin). Two gentlemen of my (and I suspect JF's) acquaintance had the dubious pleasure of jumping out of a T2 in the mid 70s for this reason.
But, the excessive Lv and inertia coupling seem to be mutually exclusive - high Lv should damp rolling oscillations, but a large SUSTAINED roll due to beta could be a problem. It sounds to me that this is a phenomenon that should be / have been seen on Concorde and the HP115. Am I right? If I am, then presumably the high alpha protection system is to prevent getting into an unsustainable high drag regime, and ultimately a large pitch-down which is likely to upset the Pax and require a fair number of thousands of feet to recover - but probably isn't related to lateral excursions?
Just idle thoughts really as I try to understand the subject.
G