[cross-posted]
FYI:
https://rcahmw.gov.uk/mapping-the-historic-boundaries-of-wales-commotes-and…
"The Royal Commission [on the Ancient and Historical Monuments of
Wales] has developed two digital geospatial layers using late-medieval
sources and historic parish boundaries to recreate the boundaries of
the commotes (cymydau) and cantrefs (cantrefi) of medieval Wales."
--
Andy Mabbett
@pigsonthewing
http://pigsonthewing.org.uk