UFC superstar Conor McGregor was involved in a physical altercation at The Marble Arch Pub in Dublin, Ireland on April 6, following a dispute about his Proper No. 12 Irish Whiskey.

According to TMZ Sports, the incident took place after an elderly man at the bar turned down a shot of McGregor's whiskey. The surveillance footage shows McGregor pouring Proper No. 12 for several bar patrons, and then taking a swig himself, before popping the old man upside the head with a swift left hand.

TMZ reports that an investigation was opened, but there is no indication that McGregor was ever charged with anything. Check out the footage in the video embedded below.

This certainly isn't the first time that McGregor has been involved in a physical altercation outside the octagon, not least the time he chucked a hand truck at a bus full of UFC fighters in Brooklyn. There was also the incident where he smashed a fan's phone outside of a Miami nightclub, although those charges were ultimately dropped.

The polarizing, 34-year old Lightweight fighter has not competed in the UFC since his chaotic loss to Khabib Nurmagomedov last October. He has teased retirement since then, but it appears as though he'll be back in action before long. UFC President Dana White has said that McGregor will fight this year, and he expects talks to pick up following the highly anticipated Khabib vs Dustin Poirier title match in Abu Dhabi next month.