Scarlets fly half Steffan Evans dances his way through the Ospreys defence.
Whilst the Scarlets under 16s cruised into the final of the WRU Age Grade Championship with a 20-12 victory over the Ospreys at Llandarcy, Blues South moved a step closer to qualification with an 8-7 win at Blues North.
Tries from Gareth George and Steffan Evans, plus 10 points from the boot of Dylan Morgan was enough to bring the Scarlets a second win over the Ospreys this season and an eighth successive victory of the campaign.
They now lead the table by nine points and cannot be caught by the Ospreys who find themselves locked in a head to head battle with Blues South to see who will join the Scarlets in next month's final.
After a break of six weeks due to the inclement weather, both sides were keen to get back to business and maintain their push for qualification. However, despite falling behind to an early Ospreys penalty by Sam Davies, it was the Scarlets who assumed control and duly turned around at half time with a 17-6 lead.
George touched down for a try Morgan converted after 20 minutes and after the latter had added a penalty, a powerful break from Jonathan Williams allowed outside half Evans to cross the line for Morgan to once again convert.
After the interval, the Ospreys had the upper hand, but failed to score the try their approach work deserved. Davies kicked another two penalties to close the gap, but the never say die attitude of the Scarlet's, and the desire to win this contest brought a final penalty from Morgan and at the same time denied the Ospreys a losing bonus point.
That loss for the Ospreys could prove crucial after Blues South moved into second place courtesy of an 8-7 win at Abercwmboi.
A Jack Dunning try and Callum Phillips conversion gave the North an early 7-0 lead, but Zac Deere's 16th minute try and a pealty from Gareth Thompson after 40 minutes was enough to see home a South side who will reach the final if they defeat the Dragons at Tredegar next Wednesday.
Team manager John Richards said; "It was a tough game and there was very little between the sides. However, our boys stuck in there and came away with a vital win.
"It's very tight, but now we must go to Tredegar next week and win."
WRU TV follows Wales' RWC training squad on day one of their camp in North Wales. The squad were greeted to an official welcome in Colwyn Bay and then headed for an afternoon of team building at ZipWorld
Brief highlights from Wales' training camp at the at the world-renowned Aspire Academy in Doha. The heat training will be combined with altitude methods once again with the players sleeping in hypoxic chambers that can replicate up to 4500m above sea level. This compliments the live high, sleep low methods employed in Switzerland.