The comma conundrum

How to use the Oxford Comma according to the Oxford style guide:

As a general rule, do not use the serial/Oxford comma: so write ‘a, b and c’ not ‘a, b, and c’. But when a comma would assist in the meaning of the sentence or helps to resolve ambiguity, it can be used – especially where one of the items in the list is already joined by ‘and’: 

 They had a choice between croissants, bacon and eggs, and muesli.

There are some cases where the comma is clearly obligatory: 

The bishops of Canterbury, Oxford, Bath and Wells, and Salisbury.

But still the controversy rages.