Conor McGregor speaks to the media while holding up his Notorious’ brand of whiskey after losing to Floyd Mayweather Jr  in their super welterweight bout in Las Vegas, Nevada, last August. Photograph: Ethan Miller/Getty Images

En route to the summit of the sport of mixed martial arts (MMA), Conor McGregor has cracked quite a few skulls. What he is finding much harder to crac(...)