Leinster secured the provincial bragging rights at the packed-out Sportsground as late tries from Shane Horgan and Denis Hickie netted them a bonus point against luckless Connacht.
MAGNERS LEAGUE: Friday, September 29
CONNACHT 16 LEINSTER 31, The Sportsground (Att: 3,678)
Scorers: Connacht: Try: Darren Yapp; Con: Mark McHugh; Pens: McHugh 2, Daniel Riordan
Leinster: Tries: Trevor Hogan, Guy Easterby, Shane Horgan, Denis Hickie; Con: Felipe Contepomi; Pen: Contepomi 2; Drop: Gordon D'Arcy
The westerners' out-half Mark McHugh was heralded as a hero last week when he landed an injury-time penalty to steal a 22-22 draw against Edinburgh, but the Dubliner turned villain on Friday night as his errors directly resulted in two Leinster tries.
Connacht came into the game having not beaten their eastern rivals for two-and-a-half years and it looked like nothing would change when, just thirty seconds in, giant lock Trevor Hogan bounded over for a try after charging down a McHugh kick.
But with Argentinian number 10 Felipe Contepomi off form with the boot - he missed three kicks at the posts in the first half - Connacht scrapped and stayed in touch. Seven steals on the Leinster lineout, with both David Gannon and Andrew Farley excelling in the air, certainly helped.
There were some flashes of brilliance from Leinster's returning Irish internationals. Looking refreshed after the Ireland squad's ten-week conditioning programme, both Horgan and captain Brian O'Driscoll were prominent in broken play.
Following a successful Contepomi penalty and despite losing Australian scrum half Chris Whitaker to a shoulder injury, Leinster managed to move 13-0 clear by the 32nd-minute. O'Driscoll flicked a beautiful pass behind his back to the supporting Jamie Heaslip who offloaded for Guy Easterby, Whitaker's replacement, to dot down.
Nonetheless, Connacht cut the gap to six points - 13-7 - by the break as Matt Mostyn combined with Galway-born full-back Daniel Riordan, who ran an excellent line, to send centre Darren Yapp in under the posts. McHugh added the easy conversion.
...Connacht flanker Matt Lacey is tackled by Leinster duo Harry Vermaas and Jamie Heaslip...
McHugh kicked two penalties to a single Contepomi effort during a dull third quarter, before the night rose to a crescendo under the dark Galway sky.
Both McHugh and Leinster prop Ronan McCormack were yellow carded just after the hour mark for scuffling, and Malcolm O'Kelly, fresh from the Leinster bench, joined them just minutes later - the Ireland lock was found guilty of killing the ball as Connacht pressed for a try.
With a man advantage, Michael Bradley's hosts quickly drew level at 16-16 thanks to Riordan's resultant penalty, but some lacklustre defending saw them falter in front of their biggest crowd of the season.
Gordon D'Arcy nudged Leinster ahead again with a drop goal, seven minutes from the end, and Horgan and Hickie, who cruelly intercepted McHugh in midfield, both waltzed over in injury-time to add some much-needed life to Leinster's Magners League bid.
Connacht: Daniel Riordan; Matt Mostyn, Darren Yapp, Gavin Williams, Conor McPhillips; Mark McHugh, Chris Keane; Brett Wilkinson, John Fogarty (capt), Ray Hogan, David Gannon, Andrew Farley, John Muldoon, Matt Lacey, Colm Rigney.
Replacements used: Adrian Flavin for Fogarty (40 mins), Ted Robinson for McPhillips (half-time), Ray Ofisa for Lacey (57), Paul Warwick for Robinson, Michael Diffley for Hogan (both 68), Tom Tierney for Keane (78). Not used: Michael Swift.
Leinster: Girvan Dempsey; Luke Fitzgerald, Brian O'Driscoll (capt), Shane Horgan, Denis Hickie; Felipe Contepomi, Chris Whitaker; Reggie Corrigan, Harry Vermaas, Will Green, Trevor Hogan, Owen Finegan, Stephen Keogh, Keith Gleeson, Jamie Heaslip.
Replacements used: Guy Easterby for Whitaker (8 mins), Christian Warner for Horgan (24-33, blood), Ronan McCormack for Corrigan (half-time), Bernard Jackman for Vermaas, Malcolm O'Kelly for Finegan, Gordon D'Arcy for Fitzgerald (all 62), Corrigan for Keogh (65-75). Not used: Niall Ronan.
Referee: Peter Fitzgibbon (Ireland)
Touch Judges: George Clancy, Leo Colgan (both Ireland)