Harlequins 5 Leinster 6: Leinster came through a tough physical battle before defeating Harlequins by the narrowest of margins in their Heineken Cup quarter-final at the Stoop to set up a semi-final encounter against rivals Munster at Croke Park next month.

Brian O’Driscoll’s side, containing five of Ireland’s Grand Slam heroes, were battered relentlessly by the home side but prevailed thanks to two penalties by Felipe Contepomi.

Points may have been at a premium - Leinster led 6-0 until the 66th minute - but it was a gripping contest played with brutal intensity.

Leinster, semi-finalists on three previous occasions, moved through the gears in the third quarter but with 20 minutes to go ‘Quins were back on the offensive.

England fullback Mike Brown dashed over but substitute outhalf Chris Malone, on for injured former All Black Nick Evans, missed the conversion.

Evans reappeared as a blood replacement for Tom Williams in a move that angered Leinster’s dug-out but the Kiwi failed with a late drop-goal attempt.

Quins will be wondering how they failed to convert their vast amounts of possession into more points.

They staged a sustained assault on the Leinster line for long spells yet the breakthrough eluded them until Brown eventually crossed.

Quins were dominant at the start of the match, with Evans missing a kickable early penalty.

Ferocious defending from Leinster halted a succession of attacks on the gain-line but their attempts to relieve the pressure were undermined by O’Driscoll and Isa Nacewa kicking out on the full.

Contepomi landed a penalty once they had escaped their half, but despite fielding an all-Ireland pairing of O’Driscoll and Gordon D’Arcy they were suffering in midfield.

The muscular Jordan Turner-Hall and his centre partner Gonzalo Tiesi created gaps while England winger David Strettle also caused problems with a positive run.

Leinster soaked up the pressure, despite Contepomi being flattened by the marauding Ugo Monye and Turner-Hall leaving a trail of bodies in his wake once again.

The stranglehold was broken by an opportunist break from Rocky Elsom at the line-out that was halted by Monye.

O’Driscoll had been quiet by that stage but the Ireland captain burst into life with a minute of the first half remaining, chipping ahead and gathering the kick via a kind bounce.

The race for the line was on but Brown and Strettle just prevented him from touching down, although number eight Nick Easter was yellow-carded at the breakdown and Contepomi was able to add his second penalty.

Worryingly for Leinster, O’Driscoll hurt his right shoulder during the move and when the second half resumed he was clearly still troubled by the injury.

The visitors appeared to have crossed through Rob Kearney in the 47th minute but Contepomi’s pass to Nacewa was forward.

Evans, back after four weeks out with an ankle injury, lasted seconds longer before limping off.

Contepomi was harshly sent to the sin bin for a an apparent trip on Chris Robshaw but the Quins flanker, who collapsed to the floor, clearly made the most of what replays showed to be marginal contact.

Neither side could take a full-blooded encounter by the scruff of the neck, although Danny Care was only denied an inventive solo try when the jet-heeled Luke Fitzgerald intervened over the line.

Quins continued to pound away at Leinster’s whitewash, the video referee saying they failed to ground the ball on one occasion.

For five minutes they camped on the visitors’ line and Leinster were struggling to halt such a sustained onslaught, eventually cracking when Brown dived over.

Malone missed the conversion and then had to be carried off, leaving Brown to fall short with a long-range penalty in the 73rd minute.

Williams was the next to leave the pitch with a blood injury, enabling Evans to return.

The Kiwi lined-up a drop goal with a minute to go but it sailed wide, allowing Leinster to breathe a huge sigh of relief.

Harlequins: Brown, Strettle, Tiesi, Turner-Hall, Monye; Evans, Care; Jones, Botha, Ross, Percival, Robson, Robshaw, Skinner (capt), Easter. Replacements: Fuga, Lambert, Evans, Guest, Gomarsall, Malone, Williams.

Leinster: Kearney, Nacewa, O'Driscoll, D'Arcy, Fitzgerald; Contepomi, Whitaker; Healy, Jackman, Wright, Cullen (capt), O'Kelly, Elsom, Jennings, Heaslip. Replacements: Fogarty, McCormack, Hogan, O'Brien, Keogh, Dempsey, Horgan.