Joshua threw Usyk's world title belts to the ground and then stormed out of the ring following his split-decision defeat in Jeddah, only to return and launch into a remarkable speech that has been criticised by many.

The Englishman, noted throughout his career for his composure inside and outside the ring, lost control after Oleksandr Usyk secured a second consecutive victory over him to defend the unified WBO, WBA and IBF titles.

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Joshua seized the microphone to vent his emotions in a passionate two-minute speech before the champion had a chance to address the crowd.

"I'm stealing this Usyk, I'm sorry, but it's because of the passion we put into this," Joshua said during his outburst.

But writing on Instagram on Sunday, Joshua admitted he let himself down.

He wrote: "I wish @usykaa continued success in your quest for greatness. You are a class act champ.

"Yesterday I had to mentally take myself into a dark place to compete for the championship belts! I had two fights, one with Usyk and one with my emotions and both got the better of me.

"I'll be the first to admit, I let myself down. I acted out of pure passion and emotion and when not controlled it ain't great.

"I love this sport so so much and I'll be better from this point on. Respect."

Joshua: 'I was in war mode'

The third defeat of his professional career clearly hit Joshua hard.

Speaking in the early hours at the post-fight press conference, the former champion was still overcome with emotion. Attempting to explain how he felt, he faltered as he choked back tears, holding his head in his hands.

"I don't feel anything," he said at first, as he tried to come to terms with the effect of the loss, before he had to admit, "I'm upset deep down in my heart."

Explaining his behaviour following the fight when he flung two championship belts from the ring, and momentarily marched out of the arena, he said: "I was mad at myself. Not at anyone, just at myself. So I thought I've got to get out of here because I'm mad. Like anyone when you're angry, you might do stupid things. Then I realised, this is sport. Let me do the right thing.

"Then I just spoke from my heart," he continued. "It's been so tough. You see AJ holding it together and I'm a hustler so I try and hold things together and I try and work hard, put things together, make sure my team's good. But it comes at a cost, a big cost. It'll never break me, but it takes real strength for it not to break you.

"There's a little crack in that armour. Because I took a loss and I think you just saw me upset.

"I'm a fighter," he added, "I'm not a normal person, even though I try to hold it together.

"I was just in war mode."

Froch: 'He stole Usyk's moment'

Carl Froch felt that Joshua deserved praise after a hard-fought 12 rounds, but had then taken the spotlight from Usyk.

"He got the mic, he stole Usyk's moment but let's not go too mad. He didn't say anything that would have offended anybody too much," said Froch.

"He was just trying to speak off the cuff. He put his heart on his sleeve but he did steal Usyk's moment and it was a bit strange.

"I didn't like the way the belts got thrown. It was a great boxing match, I thought it was a great performance. But that highlights his passion - how much it meant to him and how much he wanted it."

Clarke: 'Joshua should have been saved from himself'

Frazer Clarke, a close friend of Joshua, felt that the British heavyweight star should have been given time to retain his composure and believes his team should have done more to look after him, given the emotion of the moment.

"As a gym friend and a friend in general, for anyone that is offended by what happened, I think I can just apologise on his behalf for the outburst," Clarke told Sky Sports.

"He might be mad at me for saying this and the whole team might be mad at me for saying this, but I feel like he was left out to dry by the team. I feel like someone should have saved him.

"It's words but in the true reflection of boxing, that was Oleksandr Usyk's time to celebrate that victory and he didn't get to do it straight away. I just don't think that was right but once again, Anthony is a great person, he does a lot for a lot of people, he's done a lot for me, but I feel like he had a bit of a bad one there and it was out of character. There were no excuses, that was Oleksandr Usyk's time.

"To the people around him, where were you? Someone should have jumped in there. Someone should have stopped him and saved him from himself. It was only words, but it was the wrong time."