do you know the Bishop of Norwich

The story

Traditionally, after a vintage port has been decanted, the decanter is passed clockwise around the table until everyone has poured some. If the decanter should stall en route, it is considered poor etiquette to ask for it directly, so one must request it in a roundabout way: :— Do you know the Bishop of Norwich? :— No. :— He's a terribly good chap, but he always forgets to pass the port.