N2 East Finchley: why this London postcode has the number 2

First in the alphabet, before Finchley

East Finchley is N2 because of the alphabet. N1 is the Northern district office, and in the Post Office's list of March 1917 the offices after it follow by name: East Finchley comes first, before Finchley (N3).

See N2 on the map