I received this from Howell Gwin. The author is Stan Kegel.

A bloke and his girlfriend are having a bit of rumpy-pumpy in the back of his van. All is going splendidly until the girl starts screaming “Whip me, whip me”. The man desperately looks around for a bit of rope or cable, anything with which he can give her what she wants. Finally, he winds down lashing – much to his girlfriend’s delight!

Several weeks later the girl visits the Doctor, complaining of severe pains on her backside. The Doctor takes one look and says “I see you have been having a bit of rumpy-pumpy with your man inside his van haven’t you!”

“How on Earth do you know that?” the girl exclaimed.

To which the Doctor replied, “You have the worst case of Van Aerial disease I have seen for a long time!”