If you look in Oscar Brand's "Bawdy Songs and Backroom Ballads," You will find two variants of the song.

In the first, the central character is an innocent serving maid down on Drury Lane who meets a sailor at a dance. He sees her home with the usual result.

In the second, the waitress at the Prince George Hotel leads a protected life until a "sailor, an ordinary bloke" comes along and removes her innocence. Both end up with babies but the first version is a citation of don't let a sailor an inch above your knee and in the second, all she wishes is to keep the navy warm.