Cardiff banished their blues after failing to reach the quarter-finals of the Heineken Cup for the first time as they blitzed Glasgow to consolidate their place in third position in the Welsh/Scottish League.
Despite having to withstand considerable pressure in the first-half against a strong wind, the blue and blacks hit back with a try on the stroke of half-time to cut their deficit to two points.
Glasgow could only muster three penalties by their outside half Graeme Kiddie with the wind at their backs and as soon as Williams skipped over for his try, which Nicky Robinson converted, the game was always in their grasp.
Three more tries flowed in the second half, from Matt Allen, Gary Powell and Francois Mounier, and Robinson added two conversions and a penalty to give the home side a much needed boost with a 29-12 victory.
For Glasgow it was only their third defeat in eight games, although things are likely to get harder for them when the Six Nations comes around and puts added pressure on their leading players.
Meanwhile, at Virginia Park, Sonny Parker took the starring role as Pontypridd continued their climb up the table with a 36-16 victory over Caerphilly.
Parker ran in two of his side's three tries. Fijian outside half Nicky Little helped himself to 21 points for the visitors.
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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