Anthony Joshua has revealed a flashpoint in a London pub was the trigger for his threat to smash a chair over Daniel Dubois’ face in the build-up to Saturday’s Wembley collision.

Joshua is aiming to join Muhammad Ali, Lennox Lewis and Evander Holyfield by becoming a three-time world heavyweight champion by seizing Dubois’ IBF title in front of a 96,000 crowd.

The fuse was lit for the potentially explosive all-British clash when the rivals had to be separated by security and their promotional teams during a stormy interview in June.

Joshua was angered by what he viewed as disrespect from Dubois, but it was an incident the previous week that really encouraged him to show his teeth in a “calculated” response.

“I was in the pub. One little kid – well I’m 35 and he’s probably 30-something – thought he could say something,” Joshua said.

“You can’t let anyone think they can speak to you in a certain way because at the pub, there are other people who are looking at this person talking to me like that.

“His mate tried to show him something and he said: ‘I don’t give a f*** if AJ is here.’ I said: ‘What?! Don’t ever think you can talk like that’.

“F*** boxing, you know who I am and you know what I’m about, so don’t ever think you can disrespect me – because it won’t end well for you. So we draw a line under that. Did I leave? No way!

“Then the week after I’m doing a face-off and Dan tried to get mouthy! I’m still in the mindset where you don’t let anyone think that they can take a mile. What happens if Jarrell Miller or Deontay Wilder starts thinking they can talk to me like that?

“So, Dan, I’m gonna put a stop to you there, and listen: I will smash this f***ing chair across your face, and I’ll ram the f***ing pole down your throat!

“You have to let someone know that you’re not f***ing about, and hopefully that will ripple out to everyone else.

“I don’t want any problems, but I’m in an industry where I’m fighting. I’m not in goal, I’m not playing tennis. I’m in a sport with men with testosterone – gladiators who will take any opportunity to try to belittle you and test your toughness.”

It was a rare display of aggression outside of the ring from Joshua, who refrains from trash talk and has spent time signing autographs and posing for photos throughout the build-up to Saturday’s showdown.

But he insists his amiable public persona should not be mistaken for weakness.

“I’m a nice person, but honestly I’ll switch as well. So pick what side of the fence you want to sit on,” he said.

“Most people are all right with me, but I will definitely go to extremes that I don’t think they’re ready for. It’s up to them which way they want to do it.

“I like Dan, there’s nothing wrong with him, he’s a good guy. Remember, we’re men, we’ll shake hands after.

“But I just think it was the fact that someone thought they were okay to say: ‘We can fight now.’ Am I gonna say: ‘Nah, let’s not go now, I’m not ready.’ Are you f***ing crazy?

“I’m gonna give it back to you, and I’m gonna go to places where… It’s the industry I’m in, you have to.”