Leinster exacted a measure of revenge over Munster with a 21-16 victory over their rivals in the BKT United Rugby Championship.The sides had last clashed in last season's semi-final when a late drop-goal knocked out Leinster at the same venue.All week they had made no bones about putting things right, and after a slow and error-strewn start managed to work their way into the game and punished Munster for some sloppy play of their own.The win, secured by tries from Jamison Gibson-Park, Dan Sheehan and Jordan Larmour, keeps Leo Cullen’s side top of the table after six rounds.It was a thrilling and compelling derby, played out in perfect conditions in front of an almost full Lansdowne Road, that harked back to the good old days of the rivalry.Graham Rowntree's side will be left with frustration, however, and twice late on had worked their way into the Leinster 22 only to be let down by poor breakdown management.A crowd of 49,246 attended, most of whom were in place ahead of kick-off to applaud Johnny Sexton [below], the former Ireland and Leinster skipper, who retired following the World Cup.And anyone who was more than six minutes late missed an early try-of-the-season contender.Shane Daly fielded a high ball inside his own half and captain Diarmuid Barron's strong carry put Munster on the front foot.Garry Ringrose rushed out of the line to make a trademark hit but was too easily evaded by Simon Zebo, who set off down the wing.Calvin Nash and Antoine Frisch were in support with the centre offloading to Casey, who would have been second favourite to win his one-on-one with Ross Byrne.However, the scrum-half pushed away Byrne, who injured himself in the attempt, and dived to score.It was a devastating moment for the Leinster