Having been beaten by their closest rivals at Taffs Well earlier in the season, the South edged the verdict 13-10 to improve their chances of reaching the final.
Shaun Webber, with a try, and Lewis Williams with a conversion and penalty earned the North a valuable losing bonus point, but James Morris with a try and eight points from the boot of Rhys Patchell gave South a victory which improves greatly their position in the table.
Blues North team manager Nigel Way said; “It was a closely fought contest, but we certainly have no complaints about the final outcome.
“We played well, but they were dogged in defence throughout and deserved the win.”
The Scarlets were also in winning form – they travelled to Llandarcy and defeated the Ospreys 16-10.
Having beaten the Ospreys 41-15 earlier in the campaign, the Scarlets led 10-3 at the interval courtesy of a try from leading scorer Gethin Hunter and a conversion and penalty from Jordan Williams.
Williams then made sure of the points after the interval with a second penalty and a drop goal.
