The Mayweather-McGregor world press conference tour featured approximately 163,000 swear words, 25,673 instances of Floyd Mayweather saying "yeeeeeah," and 1 head slap by Conor McGregor. The press conferences were quite a riot.
But while fight fans had the opportunity to sit back and enjoy the fireworks, UFC President Dana White had to remain on guard, ensuring that his fighter, McGregor, didn't go too far with his promotional tactics. The slap was one of those instances in which McGregor crossed a line, and as White recalled while on Jimmy Kimmel, the whole thing played out in slow motion to him while on stage.
In case you don't remember McGregor's "peanut head" charades, here's a clip of it, complete with White's reaction.
Definitely wasn't a full slap, but White probably wasn't interested in seeing McGregor go for a second swipe at it. But while McGregor may have held back on his aggression in London, his fans certainly did not, surrounding Mayweather's car and hitting it after the press conference in what was truly a wild scene.
No need to sell us on this fight any further, we're all-in.