An open first half saw Scarlets notch three tries - Aaron Shingler, Jonathan Evans and DTH van der Merwe all dotting down - to their hosts' one through Tom James.

Hadleigh Parkes then appeared to put the visitors out of sight shortly after the interval and despite Blaine Scully's spectacular finish giving the Blues a glimmer of hope, they ultimately suffered a third Guinness PRO12 defeat in a row for the first time since November 2015.

It was the visitors who got off the perfect start on seven minutes as Rhys Patchell's dangerous, hanging cross-field kick against his old club earned the Scarlets an attacking line-out and after seven phases of persistent pressure, Shingler used his powerful frame to barrel forward and stretch out to dot down.

Patchell duly added the conversion and did the same three minutes later as Scarlets crossed again - van der Merwe superbly scooping up and darting from the base of a ruck before offloading out the back of his hand for Evans to canter over.

But barely two minutes after that score, a back-and-forth passage of play ended with the hosts going over to narrow the deficit to 14-7.

A knock-on in the visiting 22 looked to have ended the Blues' chances of a score as the Scarlets countered with pace but a loose John Barclay pass was gleefully intercepted by James, who sauntered over for his 40th Guinness PRO12 try.

The breathless nature of the derby continued and with both teams adventurously flinging the ball about, it was no surprise when another interception led to the game's fourth score on 22 minutes.

Aled Thomas plucked Steve Shingler's pass out of the air in his own 22 and reached halfway before passing to speedster van der Merwe to do the rest, the Canadian jogging clear to seemingly put the visitors on course for a fourth successive Guinness PRO12 win at 21-7 ahead.

And they held that lead until half-time thanks to some superb last-ditch defending, with the Blues spending the final ten minutes of the half camped in the Scarlets 22 but ultimately leaving pointless.

Danny Wilson's men needed to score first after the break but instead, with just 40 seconds on the clock, Scarlets wrapped up the four-try bonus point.

Patchell's dummy pass enabled him to burst through a hole in the defence on halfway and he feinted past full-back Matthew Morgan before offloading to Parkes for the score, although the missed conversion ended Patchell's 100 per cent record from the tee.

Steve Shingler's 46th-minute penalty narrowed the gap to 26-10 and when Will Boyde was sent to the sin-bin with 25 minutes left, the Blues had a glorious chance to get themselves back in contention.

They did just that as Scully collected a bouncing pass on the right and went airborne to avoid going into touch, acrobatically dotting down in the corner.

Shingler's conversion attempt sailed just wide and despite Aaron Shingler getting yellow-carded for the Scarlets soon after, the Blues couldn't close the gap any further as they suffered a third league loss in a row.

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