City of London vs British capital

City of London and British capital both are nouns.

Word	Noun	Adjective	Verb	Adverb
City of London	Yes	No	No	No
British capital	Yes	No	No	No

City of London (noun)	British capital (noun)
the part of London situated within the ancient boundaries; the commercial and financial center of London	the capital and largest city of England; located on the Thames in southeastern England; financial and industrial and cultural center