Josh Morris inspired Treherbert to their first victory in over a year in Division Three South East following their 18-13 success against Penarth.
Treherbert went through the whole of last season without a single victory to their name but Morris made sure this is a fresh start after his sprint for the try-line from his own 22.
Scott Barclay also crossed on a famous day for the Rhondda valley club who had to face a late onslaught from the Seasiders who scored two tries of their own.
And it was a day of drama in the division as Tylorstown edged a thrilling 26-23 win over Heol y Cyw.
The home side scored through John Thomas and a penalty try while 16 points from Julian Pike sealed the victory.
Tries from Richard Howells and Kevin Worgan for the visitors ensured the opening clash went down to a thrilling finale but the hosts came out on top.
Division Three East saw Pontypool United and Abergavenny produced the biggest wins of the day while Pill Harriers and Nelson nicked victories over Tredegar Ironsides and Blaina.
Pontypool United beat Newport HSOB 49-7, crossing the visitors line for seven touchdowns while Abergavenny went one better by running in eight tries against Rhymney to win 47-20.
But the Brewers were hampered when their scrum half was carried off midway through the match with a suspected broken ankle. Jonathan White went over for a brace of tries for the losers.
Ynysybwl hit maximum points on the opening day to top Division Two East following a comprehensive 34-3 victory, 6-0 on try count, over visitors Llantrisant.
Gilfach Goch, Penallta, Treorchy and Llantwit Fardre all also recorded home wins with Rhydyfelin emerging as the sole away victors 24-15 at Abercynon.
Relegated clubs Penallta and Newport HSOB met in Two East and it was Penallta who ran out winners 13-5. In the same division, Mountain Ash earned a losing bonus after running Llantwit Fardre close with a 19-15 scoreline.
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