Conor McGregor climbed off the canvas for the most stunning win of his career at the MGM Grand, downing Chad Mendes and claiming the interim UFC featherweight championship title. 

Amid the deafening noise of a partisan crowd the Dubliner had come off second-best for much of the nearly two rounds of action. But with mere seconds remaining in the second round, McGregor connected with a devastating left hand that downed Mendes for the first time in his illustrious career. 

The Californian never got up and the Irish masses who had invaded Las Vegas on a record-breaking night went absolutely wild. The heroic victory sends McGregor on a direct collision course with champion Jose Aldo for a unification clash. It also sends McGregor's star to even more soaring heights.

But for much of the fight - almost all of it in fact - it looked as if the 'McGregor show' was about to come to the most crashing of ends. Sinead O'Connor had sung the Notorious one into the ring as the atmosphere at the Grand Garden arena went beyond spine-tingling.

But once the first bell struck, things got very real. McGregor opened with a spinning kick but was quickly on the defensive. He was soon taken down to the canvas for the first time and while he worked his way out of trouble, he wasn't upright for long.

Mendes downed him again and connected with a left elbow to McGregor's right eyelid that cut the 26-year-old open for the first time in his UFC career. The round was certainly Mendes' but McGregor simply beckoned the Californian for more as the second round began.

He got more, plenty more, spending a huge part of the second round on his back but defending stoically as Mendes tried to connect with more elbows. Mendes looked for a submission but McGregor broke free, gathered himself and delivered a stunning deciding blow. 

McGregor sunk to his knees in victory and the roof all but came off the famous arena. After the marathon build-up, the change of opponent and the late switch to Mendes, McGregor had done what he has consistently done since exploding on the scene. He delivered. Delivered the biggest triumph of his lifetime.

Earlier, Cathal Pendred's undefeated UFC record did not survive the night as he was comprehensively outclassed by John Howard in what must rank as one of the most disappointing performances of Pendred's career in the octagon.

While one of the judges somehow scored the fight in the Irishman's favour, the other two correctly favoured Howard, who had the only takedown of the fight and enjoyed a strike rate that was almost three times that recorded by Pendred.  

“It was difficult for me tonight," said Pendred, tasting MMA defeat for the first time in five years. "John made it hard for me to do what we had planned on. I felt I would have the biggest advantage in the grappling but he was hard to hold down. 

"He has great hips and he’s stronger than he looks. Hats off to him. It was his night and I’ll come back better."

There was also disappointment for the third Irishman on the card, Neil Seery. The Dubliner took a unanimous decision loss against Hawaiian Louis Smolka in the second fight of the night.

Seery's arrival into the arena was the first chance for Irish fans to test their vocal chords and they duly delivered. Seery couldn't respond in kind however. He came off much worse from a first-round clash of heads and the cut eye hindered him throughout.

Apart from a first-round knockdown, Smolka was never consistently troubled and came out on top 30-27 on all three judges' cards.

“He was a lot quicker than I expected and he was excellent in the scrambles," said Seery. "His tank of gas was better than mine. Just an all-around tough bloke. I’m happy for him and I hope he goes very far in the UFC.”