If Deontay Wilder is to be Anthony Joshua’s next opponent in London this summer – far from a given – the unbeaten American will bring with him not only his lethal fists and his WBC belt but also the burden of shame after a grossly insensitive assertion that he “wants a body” on his record before he retires.

Only a couple of hours after David Price suffered a knockout on the undercard so brutal it probably ended the 34-year-old Liverpudlian’s career – laid flat on his back, unconscious, by the Russian Alexander Povetkin in the fifth round – and a few weeks since the death of the light-heavyweight Scott Westgarth, Joshua had to pause during his victory celebrations over Joseph Parker to condemn Wilder for his crassness. “I don’t condone that,” he said stern-faced of the American’s ill-considered remark. “I wouldn’t want a body on my record.”

Wilder had torn up a paid-for ticket to attend Joshua’s sixth defence and so missed being ringside as his rival was taken the distance for the first time in 21 paid fights, adding the New Zealander’s WBO belt to his own WBA and IBF decorations in front of 80,000 fans at the Principality Stadium. Wilder’s title is the last bauble needed to make Joshua the undisputed champion of the world. Lennox Lewis was the last to be so lauded.

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In the small hours of Sunday morning – appropriately enough on April Fools’ Day – Joshua expanded on Wilder’s unpredictable character and explained why his points win over a dangerous opponent with a strong chin and a big heart was exactly the way he had planned it.

When told that Wilder had reacted to his technically and strategically sound performance by saying he should remove his African tattoo because he was no Nigerian warrior, Joshua smiled. “Wilder’s Wilder, ain’t he? That’s what you’re going to get. I always say my little prayer in the corner. I pray for success and I pray for [an opponent’s] health. I even made sure I spoke to Parker’s mum before she left. I said: ‘Pat your son on the back. He did well and he’ll be back.’ Why would I want to kill her son in the ring?

“You know what? I dread the day it happens, because sometimes what you say does come to reality. I just hope it doesn’t happen to someone. [This sort of talk] is not good for the sport at all. It’s not nice to write about, is it? Once a life’s gone, you can’t get it back.

“But I’ll fight Wilder. I swear to you, it’s no problem. This is what I do for a living. But I wasn’t disappointed that he didn’t come. This wasn’t about Wilder. This was about Parker and about me. With all due respect, Wilder needs me more than I need him. It’s about being big-time, 100%. He needs British boxing. It’s way bigger here than in the States – and that’s because of us.

“You know what’s interesting? He’ll shake my hand after the fight, and respect me. So I don’t take the personal stuff to heart because I know he doesn’t mean it.”

Play Video 0:48 Anthony Joshua: 'I'll have to defend my throne again in a few months' – video

Joshua and his promoter, Eddie Hearn, say Wilder is proving impossible to deal with, though. “You don’t say you want to put someone in a body bag unless you’re purely desperate,” Hearn said. “He’s completely lost his head and he’s prepared to say or do anything to make the fight – other than actually try to make the fight. I’m not saying his team don’t want it, they’re just not making the effort.”

Joshua said: “Wilder had the WBC belt when [Wladimir] Klitschko was still fighting. If he was so interested in becoming undisputed champion, why didn’t he say to Wladimir: ‘This is the belt your brother had all these years. I’ve got it now. Come and fight me?’

“He was happy doing his own little thing quietly. He came to my Klitschko fight and said: ‘This is phenomenal. We need to be doing more of this in the States.’ But he never spoke about fighting me straight after then. And after the [Carlos] Takam fight, he called me. I asked Eddie has anything been said? Nothing. I’m in a great position because I can still fight top‑10 heavyweights. It’s not an issue. Either he’s going to step up or not. My career will still go on.

“Ten years as a pro it’s taken him to do what I have [in five years]. So you have to ask him does he really want it? We are making history time and time again. That’s why sometimes this gets boring. What more do I need to show people? It’s not about fear. It’s not about not wanting to fight anyone. But it is about doing what’s right for my career as well – not just doing what people want from you. I’m not going to give him everything he wants to get him here. He has to sacrifice a little bit as well.”

The win over Parker did not deserve the criticism it generated on social media because there was hardly a moment when Joshua was not in control. He worked methodically behind his thudding jab and watchful defence to “take the spirit from a champion”, as he put it.

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Nearly a stone lighter than in his last fight, against Takam, he moved with noticeably more nimbleness, in and out of range, and generally looked sharper. As the affable loser said: “I fought good, but he was the better man on the day.”

Parker thought the scorecards – two of 118-110 and one of 119-109, by his compatriot Ian Scott – “a bit wide”. Not many agreed. He has a rematch clause, but Joshua was so clearly superior there will not be much demand for it until Parker works his way back into the mix, possibly against Dillian Whyte this year.

Joshua, meanwhile, remains relaxed about his progress. “I don’t let the highs go to my head. If I was retiring on this high tonight, I’d be, like: ‘Yes, I’m the man.’ But I’ve got to defend my titles again in a few months’ time, so I’m balanced. We’re still hustling. It’s not time yet to sit back and enjoy the ride. I’m committed to sacrifice for the rest of my career before I can look back and enjoy it.”