Why are London Postcodes always Quoted as just EC, WC, N, E, SE, SW, W and NW?

I am not disputing that they are all London codes, and maybe as an American I do not fully understand this. However, a friend of mine was adamant she lived in Northwest London and I assumed her address code would be NW, but her address code was HA or something like that? Are there additional codes that are in... show more I am not disputing that they are all London codes, and maybe as an American I do not fully understand this. However, a friend of mine was adamant she lived in Northwest London and I assumed her address code would be NW, but her address code was HA or something like that?

Are there additional codes that are in London but not the regular ones?
8 answers 8