This song has intrigued me since it was released in 1965. The girl is obviously rich and privileged and the singer is warning her that she's getting out of her depth. All this is clear. The mysterious figure, however, is the mother. Is she still rich (heiress, St Johns Wood) or on the skids (Stepney)? If the latter, would living with her be a safe alternative for the daughter? Also, her father "took" her diamonds, etc., could mean either took them away from her (sending her from Knightsbridge to Stepney) or took them to her. I think mama is still rich but doing serious slumming, but it's ambiguous.