Lewis Robling replied for the Dragons three minutes later before Madigan punished another indiscretion from the Welsh region to help regain the three-point advantage, with nine minutes on the clock.

Madigan, who was a contender for the RaboDirect PRO12 Dream Team announced earlier this week, then added his third successful strike to give Joe Schmidt's men a 9-3 buffer.

From the restart Leinster pounced on some indecision and prop Nathan White chased a kick down the touchline though Wales international Toby Faletau defended the Dragons' try-line.

The hosts then reduced the deficit with Robling's second penalty, but Leinster roared back once more to continue the see-saw nature of the match.

Young prop Jack McGrath broke through for the game's first try. He started and finished a move involving good work from Brendan Macken and Dominic Ryan inside the Dragons 22,

Madigan's conversion made it 16-6 after 22 minutes and moments later Leinster, wearing their white away strip, almost scored their second try when Andrew Conway made a scything break but that attack was quelled.

Separate bursts from Devin Toner and then busy centre Macken punched holes in the Welsh side's rearguard before a wonderful Damian Browne offload found Conway who was denied once more just metres from the try-line.

An ambitious Madigan penalty attempt from the halfway line fell yards shy of the posts, but Leinster still took a ten-point advantage into the interval.

Dragons replacement Pat Leach almost snuck in at the corner as the Newport-based side rallied, but some brave defending from the Heineken Cup finalists helped barge him into touch.

Some bright outside back play created several opportunities and Madigan added to his individual points tally with a 64th minute penalty to extend Leinster's lead to 19-6.

Ireland Under-20 scrum half Luke McGrath entered the fray to make his first senior appearance and moments later Madigan fired over his fifth penalty of the night to leave the hosts 16 points adrift.

In the 77th minute, after a spell of pressure, Dan Lydiate crashed over from close range to reduce the deficit for the Dragons with Adam Hughes adding the extras.

Their right winger Will Harries also snuck in to score in injury-time, however Hughes' conversion attempt fell wide of the posts and Leinster stood firm to seal a narrow but deserved win.