Glasgow Warriors made it four consecutive wins in the Guinness Rainbow Cup, turning in a dominant physical performance to claim a hard-earned 15-12 victory over Leinster at Scotstoun.

Ross Thompson’s second-half penalty proved crucial, as a resolute Glasgow defence kept the defending Guinness PRO14 champions scoreless in the second half to move top of the Rainbow Cup standings for a week at least.

The early impetus was all Glasgow’s, as Danny Wilson’s men searched for an early breakthrough. A looping ball over the top from Adam Hastings sent Cole Forbes racing up the touchline, with only a scrambling Leinster defence forcing a knock-on from Nick Grigg to end the attack.

All of the home side’s early pressure eventually told with 12 minutes on the clock, however. Repeated penalties inside the Leinster 22 eventually saw Glasgow elect for the tap and go, as Fraser Brown was sent charging towards the line. Whilst the visiting defence repelled the initial drive, there was no stopping Matt Fagerson as the number eight piled over the line for the try. Thompson converted to bring up 100 points in a Glasgow jersey, extending his side’s lead to 7-0 in the process.

Yet Leinster are defending Guinness PRO14 champions for a reason, with the Irish province striking with their first visit to the Glasgow 22. Quick ball and direct running saw skipper Luke McGrath dive over under the posts on his 150^th appearance for the province, Ross Byrne converting to level the scores.

It was now the visitors’ turn to exert the pressure, hammering away at the Glasgow line as they searched for a quickfire sucker punch. Yet the Warriors defence was in no mood to roll over, the pack fronting up time and again to drive the Irish side back. Their defensive resolve eventually forced a knock-on at the base of the ruck, turning the ball over and relieving the pressure.

Leinster’s willingness to attack from anywhere was beginning to stretch their hosts, though. One such attack saw Forbes sent to the sin bin for an early tackle, with Leinster making their man advantage count immediately. Whilst good Glasgow defence initially held the Irishmen at bay, a switch in play saw Cian Kelleher have enough to hold off George Horne to touch down out wide. Byrne’s conversion rattled the upright, but Leinster led for the first time on the night.

Undeterred, though, it was the Warriors who enjoyed the lion’s share of possession as the half drew to a close. One too many Leinster infringements in their own 22 saw Rory O’Loughlin dispatched to the sin bin, meaning Glasgow would start the second half with the extra man.

Knowing a win was paramount to their hopes of a place in the final, Glasgow came out of the changing rooms firing. A turnover penalty won by Enrique Pieretto was roared to the rafters by the home side’s replacements, as the Warriors looked for the opening in the Leinster defence.

It would take a moment of sheer brilliance to unlock the visiting defence, and the home side had two men who were only too happy to oblige. Forbes was the one to make the initial break, before flipping a magnificent offload out the back door and into the arms of Hastings. The full-back duly followed suit, sending Kyle Steyn over for his third try in as many matches to level the scores. Thompson’s conversion drifted wide, but the game was very much alive.

Already being played with plenty of bite, tempers were boiling over with neither side backing down. Ryan Wilson was shown a yellow card by referee Frank Murphy for his role in a scrap, with Leinster escaping without sanction despite there appearing to be antagonists in both camps.

Once more, though, Glasgow managed the sin-bin period to near perfection. The scoreline remained unchanged until seconds before Wilson returned to the field, when Thompson made no mistake with a penalty from 40 metres to give the hosts a 15-12 lead with 16 minutes to play.

Back came Leinster once again, as the men from the RDS set about belligerently searching for their first score of the half. The Glasgow defence was equal to the task once more, though, as Niko Matawalu’s inspired rip five metres from his own line turned the ball over at the most vital of times.

No backwards step was going to be taken now by the home side, the noise inside Scotstoun rising as the seconds ticked away. Another huge defensive set in midfield forced the error from Leinster as they looked to run it from their own 22, and this time there would be no next chance for the champions. The points were Glasgow’s, and the future looks bright.