> with a postcode "N1C 4DN" we soon learn that means North London (the N), the innermost district (the 1)
N1 is innermost, yes, but N2 onwards are sorted alphabetically, and N1C isn't really more "inner" than N1.
N1 is innermost, yes, but N2 onwards are sorted alphabetically, and N1C isn't really more "inner" than N1.
There are usually 10 to 30 — if you work in a large office it probably has a postcode just for that office, for houses you share with 20-30 or so others. (Very large businesses might have separate postcodes for individual departments, e.g. an electric utility probably has one for handling bills, and another for everything else.)
"What's the postcode please?"
"N1C 4DN"
"And the number?"
"12"
Now they have the whole address. Satnav can take "N1C 4DN" and be very close: https://goo.gl/maps/sGR5XXhmUsLmD2UBA (not the best polygon, should be Handyside Street.)