Difference between はもとより and はもちろん and their respective usage I would like to know if there is some difference between and in the sense of "let alone" , "not only ... but also". On a side note, I would like also to know their respective usage (oral/written, normal/formal, modern/archaïc) > **** Children nowadays are not only forced to go to school but also scram school. > > **** There are no buses in the village where I was born, let alone trains. > > **** My school is very strict about clothes. They even warn us about our hairstyle and the length of our skirts, let alone how we wear our uniforms.

Unless you want a very strict analysis on the differences of the two, it seems to me that both mean almost the same thing when used to mean "let alone". is used more often in speech while sounds more formal/stiff and can also be used in written texts/.

A simple google search of the difference seems to agree that the two are pretty much the same when used in this context:

hinative post
chiebukuro post
Nihongo Sensei