Munster closed the gap on Magners League leaders the Ospreys on Sunday night as late tries from Justin Melck and Doug Howlett and no end of determination inspired them to an 18-0 victory over Leinster at the RDS.

South African Justin Melck was the unlikely hero as his late try swung this 131st derby match between the Irish provinces in Munster’s favour.

The reigning Magners League champions Leinster and their bitter rivals Munster, the European Cup holders, served up another epic battle in their long history, and the game was on a real knife edge until Melck touched down in the 69th minute.

The former Western Province and Stormers back rower, who is on a three-month contract with Munster, squeezed through a gap between Jamie Heaslip and Rob Kearney to send the visitors 11-0 ahead.

The coup de grace was supplied in the last-minute by All Black legend Doug Howlett, who raced onto a deft kick through from Ronan O’Gara to score under the posts.

This was Leinster’s first league defeat at home to Irish opposition in five years and the manner of the loss will worry Michael Cheika and his management team.

Having lost twice to Leinster last season and not beaten them in Dublin since that famous European success at Lansdowne Road in 2006, Munster were very keen for revenge.

As befits a rivalry which stretches back to 1876, the sheer intensity and ferocious tackling of both teams left the 18,500-strong crowd spellbound.

With neither side wanting to give an inch, Leinster debutants CJ Van Der Linde and Rocky Elsom revelled in the immense physicality presented by Paul O’Connell and company.

Munster tred to sniff out an early score but O’Gara’s drop goal attempt, after just 60 seconds, was wide of the mark.

The European champions’ lineout was a cause for concern, as it has been since the start of the season, and Leinster edged the set piece battle, with Marcus Horan struggling often in the scrum.

However, Felipe Contepomi failed to turn pressure into points for the home side.

The Argentinian star, who came into the game having landed 16 out of his 19 place-kicks so far this season, had an off-night in front of goal.

He missed penalty attempts after 4, 9 and 12 minutes, with the first two very kickable.

Munster were showing less nerves and full-back Keith Earls again caught the eye, under a flurry of high balls.

O’Gara kicked the visitors ahead in the 18th minute and the Ireland fly-half’s supreme line-kicking kept Leinster away from the danger zone.

Munster’s forwards got up a head of steam before half-time, but Leinster, with Shane Jennings on fire, absorbed everything that was thrown at them.

Cheika’s men made the better start to the second half, upping their intensity levels again, and Munster suffered a blow when Jerry Flannery went off with a shoulder injury.

But, in an attritional second period, Munster brilliantly ground their way into a winning position.

O’Gara tapped over a second penalty, close to the hour mark, and with replacement Alan Quinlan causing headaches at the breakdown, Leinster grew frustrated.

Munster’s sheer work-rate drove them on and when Mafi freed Earls for a burst down the left wing, the hosts defence was badly exposed.

The youngster passed inside for number 8 Melck who backed himself and made the line as Kearney and Heaslip were both caught out.

It was the game’s turning point and Leinster, losing at the RDS for the first time since October 2007, never recovered.

A beautifully weighted kick off the outside of O’Gara’s right boot put Howlett sliding over for his try, to confirm the sweetest win of Tony McGahan’s unbeaten Munster reign.