The 28-year-old challenger, who went into the fight as the reigning featherweight champion, added the lightweight title when referee John McCarthy stopped the bout with just under two minutes of the second round remaining.

Some fans were concerned when he changed his walk-on music to the 50 Cent tune ‘I Get Money (I Run New York)’.

McGregor changed his walk-on song before his defeat to Nate Diaz earlier this year, changed it back when he beat Diaz in the rematch.

But they needn’t have worried.

A new location but same result. The Big Apple's Madison Square Garden erupted as McGregor, with his trademark left hand causing huge damage, sent reigning lightweight champion Eddie Alvarez to the canvas three times inside the first three minutes of this much-anticipated UFC 205 headliner. Ten pounds up, the featherweight champion's punching power was clearly translating to the 155lbs division.

All Conor McGregor in Rd. 1. Seems to be the naturally bigger man. We'll see if that power corner can get Alvarez straight here.

— Jon Anik (@Jon_Anik) November 13, 2016

The Irishman, with a five-inch reach advantage over his opponent, began showboating in the second, holding his hands behind his back as Alvarez, 32, looked to respond.

It was one-way traffic and the bout was stopped when three consecutive punches knocked Alvarez to the floor and with McGregor ready to pounce, McCarthy dived in. The Garden had officially turned green.

That'll do it: https://t.co/B0gkBEcsBw #UFC205

— Paddy Power (@paddypower) November 13, 2016

Having added the lightweight title to the featherweight crown he won last December with that 13-second KO of Jose Aldo, the 28-year-old star of the Octagon said: "Not one bit (surprised). They're not on my level. You've got to have size, read, length...you've gotta have attributes. Eddie's a solid competitor. He's a warrior. But he shouldn't have been in here with me."

Taking aim at his fellow fighters in the UFC, he added: "To everybody on the entire roster, I'd like to take this chance to apologise...to absolutely nobody! The double champ does what the f*ck he wants!"

It was the 18th knockout of McGregor's MMA career, and arguably his most masterful performance, away from his renowned first round fireworks. He has won 17 of his last 18 fights, and with the Irish flag draped around his shoulders and two belts to shine up, his pulling power in the UFC shows no sign of flagging.