Blackwood opened up the title race in Division One East after edging their top of the table clash with Newbridge.
The Red, Black and Ambers toppled the league leaders at the Welfare Ground after tries from David Briggs and David James clinched a dramatic 12-8 victory.
The Newbridge advantage at the top of the table is cut to just three points and Blackwood's Lyn Hall believes the victory has opened up the division.
"This could be the catalyst for us to push on and to see what the season now holds for us" said Hall.
Leading the chase behind the top two are now Caerphilly, who capitalised on Merthyr's slip-up at Bargoed to take third place following their 22-12 victory over Ystrad Rhondda 22-12. Paul Adams and Stefan Sankala were try scorers for the Cheesemen.
Merthyr fell to fifth in the table after losing at Bargoed, who leapt above their visitors thanks to tries from Matthew Hutcheon and Geraint Hodges.
It took a last-minute try from Andrew Carlson for Rumney to break the deadlock in a tightly-fought 5-0 win over Newport Saracens, while the students of UWIC had no such problems scoring three tries in a 30-0 win at Beddau.
Carmarthen Quins had no trouble in keeping their 100 per cent record in Division One West when they hosted Dunvant.
Tries from Gavin Evans, Andrew Thomas, Alun Davies and two from Jamie Davies saw the visitors routed 27-0.
Quins picked up their sixth bonus point of the season, extending their lead at the top to 19 points.
With Tonmawr in Swalec Cup action, Narberth moved into second spot as captain Steve Martin scored two tries in their 26-15 win at Cwmllynfell.
Corus leapt above Carmarthen Athletic into fourth after beating them 34-15, Maesteg defeated Bonymaen 28-15 and Whitland saw off Felinfoel 18-12.
The last five years have been an emotional rollercoaster on and off the pitch for RGC1404. Promotion to the Principality Premiership was the culmination of five years of hard work and investment in North Wales. WRU TV caught up with prop Joe Simpson, who was one of the first intake of WRU North Wales Academy players in 2010.
Ebbw Vale captain Damien Hudd picked up the biggest accolade of the night at the 11th Principality Premiership Awards Evening held at Principality Stadium, after leading his side to the title for the first time.
Wales assistant coach Robin McBryde is predicting a tough battle against England on Sunday despite the fact they may not be considered to be at full strength. Players will be out to impress Eddie Jones which makes England a dangerous proposition, he says.
Wales U20 captain Tom Phillips and performance psychologist Dr Rich Neil explain why spending three days at Monmouth RFC has further strengthened the togetherness of the squad ahead of the #WorldRugbyU20s