Huh, I think I'll draw myself up a deed for the unregistered cricket field next to St. John's College in Cambridge. Nice area, you know.
"Elite" qualifies the owners, not the property. The Church of England and the crown are most certainly elite entities.
A family member of mine did this when the neighbours were being somewhat contentious as the official map data showed a part of her garden to be their land but the land registry people simply remarked the boundary officially on the historical wall.
Land as an attack surface.