Leinster came back from 15 points down with 20 minutes to play to keep their unbeaten record intact against a fired-up Lions in the BKT United Rugby Championship before a sparse crowd at Ellis Park in Johannesburg on Saturday afternoon.

Leo Cullen’s charges looked dead and buried when they were reduced to thirteen men when Chris Cosgrave was binned for the concession of a penalty try to leave it 36-21 on the hour.

From there, Ireland U20 Sam Prendergast, on debut, guided Leinster to 18 points without reply to snatch the winning points with the last play of the game.

The out-half’s second touch brought Dave Kearney into the game on his 150th appearance and the third put Vakh Abdaladze hurtling through a hole for a stunning try, converted by Prendergast in the third minute.

The first scrum was rock solid and Chris Cosgrave split the defence to take Leinster forward at pace again.

A tremendous turnover by Will Connors and a clever tumbling kick by second receiver Cosgrave kept the pressure on the home side.

The second score looked likely as Liam Turner, Michael Milne and Abdaladze hit the line at pace before Lee Barron lost the ball forward in contact.

A free-kick at a 5-metre scrum and a knock-on at a lineout offered the Lions a release clause they soon turned into a try when quick ball off the top of a lineout allowed Edwill van der Merwe to shoot inside in the 15th minute.

All of a sudden, a powerful Lions maul was on the move, drawing a penalty and another ominous lineout, eventually repelled when Tommy O’Brien clamped down at the ruck and kicked clear.

Brian Deeny’s athleticism at the tail of the lineout, Cosgrave’s quick feet and Prendergast’s improvisation from the boot and the hands stretched the defence.

However, the Lions’ transition game was evident when a loose Leinster pass hit the deck and out-half Gianni Lombard used back-to-back kicks and his pace to win the race for the lead try, converted by Sanele Nohamba for 12-7 in the 27th minute.

Leinster went close from Max Deegan’s burst from the back of a scrum before a sweet move along the three-quarters opened the door for Turner to blast over from outside the 22, Prendergast edging them back in front from the conversion.

It didn’t last long as Marius Louw benefitted from successive offloads by wing van der Merwe and scrum-half Nohamba, the latter converting for 19-14 in the 34th minute.

Then, a raid down the left oiled by the passing of Manuel Rass and Louw enabled number eight Francke Horn to accelerate away from the cover for Nohamba’s extras to increase the advantage to twelve at the break.

The Irish province needed the next score to mount a serious challenge, Prendergast’s raking kick taking them into the right area where the same man’s break created the go-forward for Milne to ground the ball and for Prendergast to convert in the 47th minute.

The Leinster defence was offside at a ruck for Nohamba’s penalty to make it 29-21 in the 50th minute.

When Willem Alberts cracked the first line of defence, Nick McCarthy slapped down a pass by Nohamba to be binned before Deeny ruined a Lions lineout.

However, Leinster’s indiscipline and the weight of pressure caused Cosgrave to also be binned and referee Mike Adamson to award a penalty try for 36-21 on 60 minutes.

The visitors managed the reduction to thirteen with Prendergast’s three points, Alex Soroka’s clever milking of a penalty and Prendergast’s smart decisions.

The out-half’s propensity to see and exploit space provided a fourth try for Rob Russell from a delicate chip in the 69th minute.

They were back to a full complement of players and, remarkably, looking the fresher in coming at pace for Cosgrave to sizzle through tackles and, somehow, gound the ball for Prendergast to level it in the 74th minute.

Then, Cosgrave’s out-of-this-world 50-22 had the forwards scurrying forward for a 5-metre lineout.

They were able to pound away at the line, earning a penalty for Prendergast to be the match-winner as the clock turned red.