Years ago a snowy haired anatomy lecturer used to make us cringe with his double entendres. Smutty jokes can be funny if they have a touch of wit but once they lose their freshness they are just embarrassing, even to preclinical students. That sad old man is gone now but his spirit lives on in the British advertising industry. The latest blitz from behind the admen's bicycle sheds is promoting brown bread, of all things. “Butter me up …