Dereck Chisora has slapped Vitali Klitschko across the face at the weigh-in for their WBC heavyweight title fight on Saturday.
The two fighters squared up after stepping off the scales, as is tradition, but Chisora, nicknamed Del-Boy, lashed out at the champion, who then needed to be held back by his team.
Chisora's own trainer Don Charles condemned the Englishman's actions as "unacceptable", while the actions seemed to surprise and confuse promoter Francis Warren.
"We're all scratching our heads about it, to be honest," said Warren, representing his father Frank's company.
"You always expect something from Dereck - he's a character - but it's usually something that winds people up or is a bit jovial.
"So for him to get physical and aggressive, unprovoked, is surprising. But I'm sure there's method to his madness and we'll find out if the madness has paid off tomorrow night."
Chisora weighed in at 17st 3lbs while Klitschko came in at 17st 6lbs.
