Llanharan made light of the wind and rain to complete a notable double over league leaders Llangennech at the Dairy Field.
Six points from the boot of Chris Williams with the elements in the first-half laid the platform before second half tries from flanker Scott Malone and left wing Josh Austin completed a notable triumph .
Llangennech's defeat meant that Narbeth had the chance to go top and they grabbed their opportunity with a 20-18 away win at basement boys Tondu. But it took a last gasp penalty from Nick Jones to secure the victory.
Mark Roberts crossed first for Tondu, with David Griggs adding a second try, and with Dean Thomas adding a penalty and conversion the home side were 15-7 to the good at the break. But No 8 Jim Kaumahotoya's first half try was added to by centre Steve Martin and Jones' final act eventually won the day for the visitors.
Diggy Bird's nerveless kicking proved the difference in TATA Steel's 13-7 win away at Bridgend Athletic that moved them up into second place in the table. Each team scored a try a piece, winger Tylan Mafi crossing for TATA and centre James Olds replying for Athletic. But it was former Wales Under 16 cap Bird's two penalties and a conversion which made the difference in a good away win.
UWIC ended a poor run of form with a five try demolition of Ammanford in a mid-table battle. An awesome performance from the pack saw the students dominate proceedings and pack members Jordan Saunders, Nick Halse, Craig Howells and Kyle Tayler were all on the score sheet.
Mark Cooke added four conversions and two penalties with winger Pierre Tucker crossing for the fifth try. Prop Samson Lee went over for Ammanford, but they were well beaten.
Carmarthen Athletic secured a bonus point win with a 34-7 win away at Waunarlwydd. Try machine Pan Rashesha was again among the scorers as was fellow wing Luke Marshall. Gareth Bennett, Tom Sloane and scrum half Scott Maynard completed the rout and Maynard took his match tally to 14 points with nine from the boot. Hooker Matthew Wedlake's first-half score for the home side was their only consolation.
After two wins in their last three outings in November lowly Bonymaen travelled to Whitland hopeful of picking up some more points and they battled bravely in the first-half. But they finally went down 14-8 and had to be content to leave with a losing bonus point. with Whitland before finally succumbing to a 14-8 defeat.
No 8 Jack Mason scored for The Borderers and two penalties from fly-half Nicko Setaro and one from Scott Newton proved the difference. Paul Cunniffe grabbed a try for Bony and Paul Warlow kicked a penalty.
SWALEC Division One East
Ebbw Vale once again displayed their title credentials with a comfortable win at mid-table Beddau in Swalec Division One East.
The Steelmen, the defending champions, took a winning bonus point - their 10th of the season - from the 28-12 victory at Mount Pleasant Park thanks to tries from flanker Nicky Coughlin, wing Tom Ashmead and full back Charlie Simpson, as well as a penalty try. Outside half Dorian Jones converted all four scores.
Bargoed kept up the pressure on the leaders with a four-try performance of their own. The second-placed side convincingly saw off Mountain Ash with a workmanlike 28-0 triumph at Bargoed Park. Tries for the hosts came from centre Rhys Humphries, wing Lee Pearson, prop Lewis Wayman and outside half Matthew Hurley.
The result of the day belonged to Glamorgan Wanderers, who produced an impressive second-half display of their own to recover from a six-point deficit to take a 22-9 win over Newbridge, who slip to fourth place in the table. Wanderers' tries came from wingers Owen Marshall and Dan Lovell as well as centre Joe Xiberras.
Gilfach Goch climbed above Newbridge thanks to a clinical 30-6 success over Rumney at Welfare Park. Centre Shaun Roberts crossed for a double, with No 8 James Locke touching down for a third. Full back Ian Davies added 15 points from the tee, but the poor conditions hindered the home side's search for what would have been a fourth, bonus-point try.
Meanwhile, Treorchy belied their record as the division's joint lowest try scorers by notching up four in a devastating second half showing. The Zebras trailed visitors Merthyr 15-3 at the break but a brace apiece from centre Trystan Lazarus and wing Peter Hutchings - as well as 14 points from the boot of Celyn Ashton - gave the hosts their seventh win of the campaign.