Could someone provide (ideally documented) evidence for the following details of the possible meanings/connotations of the word "boy" as used by a start-of-20th-century upper-class British person of liberal social persuasion.
The exact person is probably irrelevant, but in case it helps to clarify the answer, its John Maynard Keynes.
The specific questions I have are:
What were the standard connotations of using the word boy by a British person of Keynes linguistic type (e.g. upper-class Briton, socially very liberal, at the start of 20th century).
How likely is it that the word "boy" was used to refer to an of-age adult (say above 18 years old) in general language usage?
Is there any possible evidence that "boy" may have been a slang for adult (over 18) male prostitute, in the slang of either Keynes's typical language usage, or more specifically, British upper-crust homosexual culture of the time which presumably had its own slang like any subculture does.
In case the question seems peculiar, it arouse out of trying to parse a quote in Keynes's letter referring to "Tunis, “where ‘bed and boy’ were also not expensive.". Please note that the letter was addressed to his homosexual lover, to provide context for the third question above.
It was claimed that it is impossible - merely from the word "boy" - to discern whether he may have meant a of-age prostitute or underage one. I am looking for linguistic reference to support either view (e.g. if someone can show that there indeed was slang usage that didn't imply underage; or vice versa that there's no linguistic evidence that there was any chance of him speaking of adult males).