[rewboss]

You're looking for the "Oxford comma" which, despite its name, is more common in the US than in Britain.

Opinion is divided on the Oxford comma. Some say it is always necessary, some say it should never be used, but I think most would agree that it is not always necessary, but sometimes it is.

Here it isn't necessary because the sentence is easily understood without it. But here's an example where it certainly is necessary:

My favourite flavours of crips are: smokey bacon, roast chicken, prawn cocktail, and salt and vinegar.

Without the comma before "and", it would be unlear whether the penultimate item was "prawn cocktail" or "prawn cocktail and salt".

In your sentence, there is no such ambiguity. But you might want to check up on the house style: some publications insist on the Oxford comma, so as a proof-reader you'd have to insert one.