The Scarlets had their pride dented as Leinster, rival candidates for the PRO12 play-off spots, grabbed a bonus point in a 32-5 victory in Dublin.
The hosts scored tries through Andrew Goodman, Aaron Dundon, Jordi Murphy and John Cooney.
Andy Fenby touched down for the Llanelli side's only try, as Leinster added 21 unanswered points after the break.
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Rain moving east, heavy at times
The Lesbian, Gay, Bisexual and Transgendered communities in Cardiff are celebrating 30 years of campaigning; as part of LGBT History Month.
Cloudy at first, with outbreaks of rain gradually easing during the morning.