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."
The WRU has launched a campaign to create a long term legacy for Welsh club rugby by highlighting the advantages of volunteering. Rhian Edwards, a volunteer at Seven Sisters, has enjoyed many benefits of her volunteering at a grassroots rugby club including being part of the Rugby World Cup volunteer workforce after being nominated by the WRU - and the WRU is asking for more people to develop their 'Welsh rugby roots'.
Wales head coach Warren Gatland and captain Sam Warburton say their first prioirty on Sunday in the opening game of the World Cup is to win against Uruguay and not get overly concerned with points difference.
With only days to go until the biggest rugby competition in the world begins, rugby fans visiting Cardiff this autumn will be able to enjoy a special display at National Museum Cardiff as part of the celebrations surrounding the Rugby World Cup.