Cheeky Conor McGregor waited until the very last meeting with Floyd Mayweather to break the no touch policy inserted in his fight contract.
McGregor, who faces Mayweather on August 26 in Las Vegas, was warned no to lay a finger on the American throughout the duration of the press tour, although the Irishman couldn't resist.
Despite several head-to-heads completed without any contact, McGregor decided to test Mayweather's patience in London with playful rub of the head.
Clearly irate, Mayweather attempted to immediately laugh off McGregor's actions but moments later was staring at his forthcoming opponent with daggers for eyes.
It's not yet known, nor will it be made public, whether Mayweather will pursue any punishment for the McGregor pat - which was accompanied by a 'slaphead' slur for the 'Money' man's trouble.
Mayweather and McGregor will finally trade blows in six weeks time on the back of the most-watched press tour in combat sports history.
Over 50,000 fans witnessed the media gatherings live, whilst millions tuned in to Showtime and UFC's live streams of the events.
There was some uproar in the UK on the final leg though as Showtime scrambled their feed in order to please ITV Box Office's free transmission.
ITV also decided to censor the swearing between Mayweather and McGregor, although fans were saved by the UFC, who televised the London presser without bleeps on their YouTube channel.
Watch the video here and click on 1:38 mins to view McGregor's head rub