Sioned Harries scores her first try against South Africa under a pile of bodies.
A hat-trick by barnstorming Number 8 Sioned Harries paved the way for Wales Women to win their first World Cup pool game since 1998, when Rachel Taylor's side defeated South Africa 35-3 at Marcoussis.
Replacement prop Jenny Davies was the other try-scorer as Wales romped to a bonus point victory - although they left it late with Harries completing her hat-trick on the stroke of full time.
Centre Robyn Wilkins brought her kicking boots with her as she added the extras for three of the four tries and added two penalties while fly half Elinor Snowsill slotted a smart drop goal in the first half to set Wales on their way.
Both sides went into the match having lost their previous two pool games and knew a third loss would give them the wooden spoon for the group.
Wilkins and Zandile Nojoko traded early penalties before Wilkins and Snowsill edged Wales in front with a penalty and drop kick.
The Welsh pack stood up to the bigger South African pack where prop Mega York proved a particular thorn in the side, both in the set-piece and in the loose. Captain Rachel Taylor led from the front in defence as South Africa showed glimpses of their ability but Wales' defence held firm.
A turnover on the South African line allowed Wales Harries to plunge over for the game's first try and with Wilkins adding the conversion, Wales went into the break 16-3 ahead.
Davies then plunged over from short range as Wales hunted for tries. Harries bagged her second try when she exploded from a scrum to crash over.
Wales hammered away at the South African line and their patience was rewarded in the final play of the game when Harries somehow dived over in the corner with two defenders hounding her.
The Welsh pack were outstanding individually and as a unit with Taylor exceptional once again. Harries was always a threat with the ball in hand while York proved difficult to bring down with her bullocking runs.
The second row of Jenny Hawkins and Shona Powell-Hughes were also immense.
Halfbacks Sian Moore and Snowsill were composed while the back three of Adi Taviner, Laurie Harries and Dyddgu Hywel constantly looked dangerous with ball in hand.
Wales head coach Rhys Edwards paid tribute to his side who he said finally got what they deserved.
"Deep down we've known that performance was in us. We were unlucky in the Six Nations where we were on the end of some disappointing results," he said.
"Once you are in that short of spiral it is difficult to come out. But we've kept banging away at the door and we knew one day we would get the result. It's very pleasing that the girls went out and executed the game plan perfectly against South Africa. It certainly feels like a weight has been lifted off our shoulders."
Beating Merthyr has boosted Carmarthen Quins hopes of reaching a top eight spot in the Principality Premiership. Quins captain Haydn Pugh is delighted with his team's progress and is determined that everyone from the Under 6s through to the senior team, enjoys the ride.
When the Wales squad were asked to nominate individuals who played a big part in their early playing days, Wales and Dragons full back and wing Hallam Amos thought of his former Monmouth School rugby coach John Bevan.
Sam Cross and Luke Treharne have been named as co-captains of the Wales Sevens side as head coach Gareth Williams names his 12-man squad to play in the first leg of the HSBC World Series in Dubai next weekend.
Bedwas head coach Steve Law and players Nicky Griffiths and Alun Rees extol the virtues of the close knit club as they prepare to host third place RGC 1404 - who are one place head of them on the Principality Premiership points table - on Saturday.
Many of the Wales squad have said Diolch (thank you) to someone who played an important part in their early playing days by nominating them to be invited to the Wales v South Africa match. One person, Gowerton Comprehensive geography teacher Mr Dean Mason was nominated by two of his former pupils, Dan Biggar and Sam Davies.
The second WRU disability rugby pilot has been delivered, this time in Caerphilly schools, culminating in a festival at the Caerphilly Centre of Sporting Excellence, Ystrad Mynach tomorrow. Plans are in place to set up a Disability Rugby Club in Newbridge to provide long-term playing opportunities.
WRU TV: Hear from inside the Wales camp as Neil Jenkins discusses this weekend's clash with South Africa and how the squad are looking to put in a strong performance to round of the 2016 Under Armour Series