Conor McGregor celebrated his 29th birthday by defending himself against accusations of racism during a media tour to promote his fight with Floyd Mayweather in London on Friday.
The Irish mixed martial arts fighter went on the defensive at the fourth press conference in as many days with American Mayweather at the SSE Arena, Wembley.
The pair meet in a light-middleweight boxing contest at the T-Mobile Arena in Las Vegas on August 26 in what could be boxing's richest ever fight.
But the event has received some negative publicity since McGregor said to Mayweather at a press conference in Los Angeles on Tuesday, "Dance for me, boy".
"If he feels disrespected he's an idiot and **** him as well," McGregor told reporters at a press conference.
"I think it's ****ing ridiculous. I don't understand it. I know who I am as a person. Most realistic people can see that. He’s trying to sway something by (saying I’m) disrespecting women.”
Before going on stage in London, American Mayweather criticised McGregor for what he perceived were racists comments made by the Irishman.
"Racism still exists," said Mayweather, 40.
"I’ve got a diverse team. It’s all about treating people how you want to be treated. You have to give respect to give it back.
"He totally disrespected black women, he called black people monkeys and he was disrespectful to my (13-year-old) daughter.
"I’m not going to stoop that low to talk about his wife or child. There’s certain levels and you don’t stoop to or cross. I love everyone."
Their latest trash-talking exchange was full of profanities and insults, just like the previous events in New York, Toronto and Los Angeles.
Both claimed victory in the war of words.
"I smoked him in all four rounds," McGregor said.
"In the first round, they set me up with no music or anything. The **** you suit I wore went viral. Toronto was a wipeout, a 10-7 round, and New York was alright, and tonight I smoked him so it's 4-0, or 3-1 if you want to be generous."
But Mayweather, who has not fought since September 2015, believes he got the better of McGregor.
"I’m the best at it, when it comes to trash talking,” Mayweather said.
"He's not able to push my buttons. He cannot out talk me.
"There has been a lot of trash talkers (through his career) and at the end of the day, he's not bad.
"We will rate him number two, I'm number one. He's got heart. You need more guys to be more aggressive to each other, do more trash talking to each other."
By day four in London, some of the lines had already been heard, but not that the estimated crowd of 10,000 at the SSE Arena cared much. They lapped it up and cheered, but only for McGregor.
Mayweather, a five-weight world boxing champion who knocked out Briton Ricky Hatton in 2007, was booed loudly by the fans, many of whom were Irish, and he could barely be heard.
The pair met on a makeshift stage, a boxing ring, in the middle of the venue.
"This is my first time in a boxing ring, and in six weeks I run boxing,” said McGregor.
"Four years ago I fought in front of 400 people. Now I get to quadruple my met worth for half a fight."
At one point McGregor walked behind Mayweather and rubbed his head, before calling him a "bald" profanity and then throwing the microphone in the air.
Their fight could be the richest in boxing history, making more than the $623.5 million generated by Mayweather-Manny Pacquiao in May 2015.
Mayweather, who has earned approximately $700 million in his boxing career according to Forbes magazine, is the best boxer of his generation and has won world titles in five weight classes and is looking to extend his unbeaten record to 50-0.
McGregor, a UFC featherweight and lightweight champion, has never had a professional bout and is a big betting underdog, but can still expect to make $100 million from the fight.