Floyd Mayweather was involved in heated exchanges with Liam Walsh's brothers as a press conference to promote the Briton's world title bout against Gervonta Davis turned ugly.
In his promoter's guise, America's Mayweather is accompanying his protege and compatriot Davis in London, where he makes the first defence of his IBF super-featherweight title on Saturday.
Their preview of the fight was consistently interrupted by provocations from Walsh's brothers Ryan and Michael, and Mayweather frequently responded, shouting "I'll slap both of you pussies" as both parties threatened to lose control.
Mayweather also said: "I'm 40 and I'll beat all three of your asses on the same night" while Davis laughed at his promoter again taking centre stage.
Liam's twin brother Ryan - each turned 31 on Thursday - shouted at Mayweather from the back of the room about how he has never fought outside of the United States.
And in further retorts Mayweather responded: "Frank Warren (Walsh's promoter), why did you even sign these two p*ssies? Both of them are bitches.
"This isn't even your press conference: get the f*** out of here.
"I better not catch you in the US. You better get those two little leprechauns out of here before they get slapped.
"Last time you had an undefeated fighter over here was Ricky Hatton and you know what I did to him? I knocked him out."
Turning his attentions to Liam Walsh during the fighters' face-off, Mayweather also said: "You're a super-cold bum: you're going to get that chin tested."
Unlike his brothers, Cromer's Liam Walsh remained remarkably composed for someone preparing for his first world title fight against one of the world's most promising fighters and who was consistently backed up by an all-time great.
After Mayweather had discussed the way the 22-year-old Davis has pursued a glamorous lifestyle similar to his, Walsh said: "We're complete polar opposites. Some people are that poor that all they have is money. I'm not that poor.
"My family, my happiness, my health is paramount in my life and that's all that matters to me. Everyone needs money but it's important to have your focus and your true values on other things.
"I'm not one bit intimidated, not one little bit, not by Floyd, not by 'Tank' (Davis' nickname), not by anybody. Not by no man."
Mayweather again reacted, insisting: "We'll take your cheque.
"One thing I learned, when it's time to cut the lights off when the bills are due, you can't go tell the bill man 'I love you' and they'll keep the lights on, so remember that. We'll have you as a fighter because you want to fight for free.
"I'm known for dishing it out. I already conquered your country once (against Hatton in 2007). We're going to conquer it again on Saturday."
Ryan Walsh also fights on Saturday at the Copper Box Arena, where he defends his British featherweight title against Marco McCullough.