Neil, if you are confused about the 'Bishop of Norwich':

If a guest fails to pass the decanter on to his or her neighbour, it will come to a standstill.

This usually happens because a guest does not notice that the decanter is there, does not realise that they should pass it on or, more rarely, hopes that no one will notice so that they can have a second glass.

Guests waiting further down the table for the decanter to arrive may become impatient. However, it is considered bad form to demand that the decanter be passed on. Instead, the person who is preventing the decanter from continuing its journey round the table is asked politely ‘Do you know the Bishop of Norwich?’ This is a gentle reminder to get the decanter moving again. If the meaning does not sink in, the less subtle alternative ‘Is your passport in order?’ may be used.