Sad but true, the noble Oxford comma is being unceremoniously dropped from the Oxford Writing and Style Guide. Here is an explanation of the new recommended usage, which is I think very similar to Lynne Truss’s preferred usage from Eats, Shoots and Leaves:
Here’s an explanation from the 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’ [for example]: They had a choice between croissants, bacon and eggs, and muesli.”
Good ol’ Ox, your vast and far-ranging contribution to pernickety punctuation sectarianism will be sore missed…
You can read the whole story here.