... and i can tell you all about male constancy , i can ... `` but , my dad ... what ... '' `` your father says he 'll agree to let you go , but only if you swear on your sacred honor that you will place yourself under my grandfather 's guidance as regards your personal behavior , and i agree with him on this-i know , i know , i sound like a hypocrite-but there are many pretty boys in london and boys lie , oh , yes , they do .