Official reference
ONS Index of Place Names
The Office for National Statistics uses the historic counties in its Index of Place Names for Great Britain.
The Index records historic county, council area, lieutenancy area and other classifications as separate geographical layers, and points directly to the Historic Counties Standard.
Why the ONS reference matters
Four parts of the evidence
The Index matters both because it uses historic counties in practice and because it identifies the published county definition on which that field is based.
Official working dataset
Historic counties in the ONS Index
The Index uses historic counties as a reference for real places across Great Britain, alongside council areas, lieutenancy areas and other official classifications.
Boundary basis
The Historic Counties Standard
The User Guide identifies Definition A of the Historic Counties Standard as the basis used for the historic-county field, giving the boundary reference a published definition.
Stable geography
A long-standing reference
The User Guide treats the historic counties as long-standing geography and recommends them as a stable reference covering the whole of Great Britain.
Separate layers
Historic county is not council area
Because the Index records historic county, council area and lieutenancy area separately, it makes the distinction between those geographical layers explicit rather than implied.
An official reference point
The ONS guide shows historic county geography being used in practice
The Historic Counties Standard explains the geography in depth; the ONS Index of Place Names shows that defined geography being used in an official national reference product.