The Ospreys had trailed from the first minute, and with 30 minutes to go were in need of two converted tries, but they dug deep to upset the odds, taking the lead for the first time with less than three minutes to go having survived 10 minutes with a man in the bin after Justin Tipuric had been yellow carded just after the hour.

A penalty for offside in the midfield inside the first 50 seconds offered Leinster a chance to open the scoring, Fergus McFadden slotting over a simple kick.

Despite the early setback the Ospreys didn't appear fazed at a capacity RDS Showground, and they got their first points in the ninth minute, Biggar with the penalty after Nathan White was pinged for not rolling away.

The opening stages were very stop-start, the game taking time to really get going, but Leinster had another chance to for goal after Ryan Jones was penalised for the same offence as White, but McFadden's kick was always going to the left of the posts from the moment it left his boot.

As the game began to settle into some kind of rhythm, with the hosts on top, a big Hanno Dirksen hit on Isa Nacewa was a clear indication that the younger Ospreys in the line-up were not going to be overawed by their surroundings, before the Leinster scrum went backwards at a rate of knots under pressure from the visiting eight.

However, at the next scrum Paul James was penalised, allowing McFadden to put his side back in front midway through the first half before the centre's huge wind-assisted kick from just inside his half took the score up to 9-3.

At the half-hour mark Biggar won good turnover ball just inside opposition territory, allowing the Ospreys to counter, eventually leading to a penalty after Luke Fitzgerald came into the ruck from the side. Unfortunately for the Ospreys though, Biggar pulled it to the right of the sticks.

The first try of the game went Leinster's way in the 33rd minute, and it was a score that came with a fair share of fortune about it. Richardt Strauss overthrew at the lineout and it looked as though George Stowers was going to gather the bouncing ball only for Leinster's alert fly-half Ian Madigan to rush through and pounce, racing through to score. McFadden successfully converted.

The Ospreys responded positively and Biggar slotted over his second penalty a couple of minutes later after Jamie Hagan was pinged at the scrum.

HALF-TIME: LEINSTER 16 OSPREYS 6

Although they were trailing, the Ospreys would have been relatively happy with their first half performance. However, it was imperative that the Ospreys got off to a bright start but the first break came from Fitzgerald, the wing coming infield to sidestep Tipuric before scything through a gap in the Ospreys defence. As Fussell brought the wing down, Tipuric recovered well to get back and win the turnover.

Just four minutes after the restart an unfortunate, but accurate, offside call against Tom Smith allowed McFadden to take Leinster's lead back to 13.

The Ospreys came back at Leinster, enjoying their best spell of the game as the forwards worked their way towards the line with a series of pick and go's before Ryan Jones was penalised for holding on as he found himself isolated.

A fantastic break from Richard Fussell, taking the high ball in his own half and immediately running it back at Leinster, eventually resulted in an attacking scrum beneath the posts. A second penalty against Hagan saw Biggar slotting over a simple kick, and it got better for the Ospreys just a minute later thanks to a wonderful try from Stowers.

It stemmed from quick ball at the breakdown, the number eight himself finding Beck who carried well before feeding Dirksen on the wing. The young centre stayed with him to receive the return pass, and with the Leinster defence expecting him to go for the line he just slipped it inside for the supporting Samoan who went over for his first score in Ospreys colours. Biggar's conversion meant that the Leinster lead had been cut back to just three points.

The score rattled Leinster into life and they hammered on the Ospreys line, strong running from McFadden sparking them into life. Dave Kearney was stopped just short before referee Peter Fitzgibbon ruled that Heinke van der Merwe had been held up over the line.

A tremendous shove from the Ospreys pack at the resulting scrum saw Leinster going backwards, but the ball was moved away from the base quickly. Again, the Ospreys defended well, and as van der Merwe tried to barge his way over from close range, the loosehead was again held up, the TMO confirming that Beck had done a tremendous covering job to get across and prevent the grounding.

The pressure had to tell eventually, a penalty finally going way Leinster's way, and after a long delay due to an injury to Hagan, McFadden's boot made it 22-16 with an hour gone.

There was a big blow a minute later when Tipuric was sent to the sin-bin for an alleged tip-tackle on Kevin McLaughlin, but there was no double punishment as McFadden's long-range effort into the wind fell short.

Despite being a man down the Ospreys were still in contention, less than a converted try behind, and some good interplay almost saw Ashley Beck put through to score out wide on the right only for play to be brought back for crossing.

The 14 men were in control, the 10 minutes they were without Tipuric being played out almost entirely in Leinster territory, but immediately upon his return the Ospreys found themselves defending a scrum on their own line after Dirksen was forced to take it back as he tidied up a Sean Cronin fly-kick upfield.

With the Ospreys dominant in that area of the game they were able to drive forward, winning a penalty, and having gone upfield, were awarded another scrum which again inevitably resulted in a penalty.

With just three minutes remaining it seemed as though the initiative was with the visitors as they chased an unlikely win, and again the Ospreys pack provided a platform to work from, allowing Beck to sidestep and jink towards the line. Tipuric provided support, before the ball was flung out wide to Hibbard hugging the right touchline.

The hooker had a lot of work to do but in typical fashion he barged his way forward, looking for the try.

It looked as though he had been held up as he looked to ground, but the TMO scrutinised the footage, and eventually was able to see the end of the ball being dotted down as Isaac Boss looked to turn Hibbard onto his back.

With the try awarded, the Ospreys were trailing by a single point, leaving Biggar kicking to win the game. It was a tough ask from right out on the touchline, but he sent it goalwards and it struck the upright before coming down on the right side of the sticks, the touch judges flag confirming that the Ospreys had the lead at last.

The inevitable final flurry of pressure came from Leinster but the Ospreys were able to keep their discipline and hold out their hosts for the closing seconds to secure a stunning and memorable win that means their hopes of a home semi-final in May remain very much alive.