The election was held following the death of Karen's late husband, Alun Davies.
In numbers, the results were as follows:
Karen Davies, Plaid 747
Tom Fallows, Labour 239
Aled Crow, Tory 146
Caryl Tandy, LibDem 14
The haemorrhaging of support for Labour in Saron follows a disastrous performance in nearby Iscennen ward and another dire result in Burry Port, all masterminded by Rob James who ousted Jeff Edmunds as leader of the Labour group in a coup in May.
Readers will recall that Rob James launched a vitriolic and highly personal attack on Jonathan Edwards MP, the council leader Emlyn Dole and other senior Plaid figures immediately before the Iscennen by-election, with the publication of claims that a £145,000 regeneration grant in Ammanford "may" have been improperly awarded.
The Wales Audit Office has now rejected Rob James's complaints and announced that it will be taking no further action.
Instead of apologising for what looked very much like an attempt to throw an election with a smear campaign, Rob's response to finding himself in a hole is to keep digging. He is now questioning the WAO's findings and has announced that he will be contacting the Cabinet Secretary to call for a full investigation.