Cardiff's primary rivals for the Premiership crown both slipped to defeat, as Swansea and Cross Keys dented Llanelli and Newport's title chances.
Previous league leaders Llanelli were beaten 31-23 at St Helens, with Leigh Bevan grabbing two tries for the All Whites. Nicky Thomas scored the decisive try through a length-of-the-field interception, while James Dixon impressed with the boot. Llanelli scored tries through former Swansea captain Matthew Bradley and Simon Peters but defeat means they now sit three points behind Cardiff having played a game more.
Newport experienced their eighth loss of the season as Cross Keys left Rodney Parade with a stunning bonus-point win. Marcus Johnstone was the hero with a hat-tick of tries for Keys who turned a 12-10 half-time deficit into a convincing 32-17 victory.
At the bottom of the table, Pontypool claimed only their seventh win of the campaign thanks to an impressive performance at Ebbw Vale. Geraint O'Driscoll kicked 19 points for the visitors as Pooler gave their chances of Premiership survival a huge boost with a third successive victory. Having beaten champions Neath a week earlier, Ebbw entered the game in high spirits but early tries from Sam Mills and Adam Brake helped Pooler to a commanding 19-5 half-time lead, with only a Richard Jenkins try troubling the scoreboard for Vale. A Mark Jones try gave The Steelmen hope but a Tom Edwards score and 10 second-half points from O'Driscoll saw Pontypool home.
Llandovery also gave themselves real hope of avoiding the drop after recording a vital 22-19 win over mid-table Glamorgan Wanderers. A late try from Lee Williams saw the Drovers edge a se-saw battle that allowed them to move out of the bottom two. Matthew Jacobs was the other Llandovery tryscorer, while Josh Navidi crossed for the Wanderers before Williams struck with seven minutes left to play.
Elsewhere in the Principality Premiership, Pontypridd continued their recent good run of form with a 28-7 win at Bridgend. Grant Harrington, Lewis Williams and Nathan Strong claimed tries for Ponty as they recorded their fourth victory in five games.
In the two fixtures played on Monday and Tuesday of this week, Neath and Ebbw Vale saw off Aberavon and Swansea respectively. Neath ran out 19-10 winners to move five points clear of Aberavon, while Ebbw jumped ahead of Swansea into eighth place thanks to an 18-5 win at Eugene Cross Park.