Mike Costello
BBC Sport boxing correspondent on Radio 5 Live

This is of huge significance of the career of AJ, but also for British boxing. He has been the tide that has raised all boats since he won gold at the London Olympics.

He is the leading figure in British boxing and another defeat severely dents his career, and that boom in British boxing.

Promoter Eddie Hearn told BBC sports editor Dan Roan that "there are so many hypocrites" over the fight taking place in Saudi Arabia and said that "no-one can tell a fighter where they can and can't go to earn money".

Luke Reddy
BBC Sport in Riyadh

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It wouldn’t be right if I didn’t tell you a bit about Riyadh.

Firstly, the food is tip top. Here’s a platter we’ve tried twice and still haven’t been able to finish. Those are Steve Bunce’s feet by the way.

The city itself is a mix of old, dusty buildings and the new age skyscrapers you may see in Dubai.

A lot of people haven’t liked the fact boxing has come here. Many though may have to accept that money talks and this nation seems intent on using it to do so.

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Andy Ruiz Jr's mum blows a kiss to her son. He has just become a world champion and declared their struggles over.

Ruiz's trainer Manny Robles is sobbing, pointing to the heavens and praising the guidance of a dad he lost 12 years ago.

This is the dream.

A short walk away, in his Madison Square Garden dressing room, Anthony Joshua is told by his father that he must "go back to the drawing board".

Joshua's best friend, David Ghansa, wipes away tears.

This is the nightmare.

Luke Reddy goes inside the 24 hours that shook boxing, read how the night in New York in June unfolded here.

Mike Costello
BBC Sport boxing correspondent in Riyadh

At his training base in Sheffield this month, Joshua recalled how the left hook landed by Andy Ruiz Jr in the second minute of the third round marked the beginning of the end of his debut at Madison Square Garden. There was more than half the fight remaining - the referee waved it off in the seventh - but in Joshua's mind it was all over much sooner, along with his reign as world champion.

Earlier in the third round, Ruiz had been floored by a right-uppercut, left-hook combination and Joshua went looking to land the same two shots twice in the following 20 seconds. On the second occasion, as Joshua swivelled into his left hook, Ruiz got there first with an almost identical punch. Joshua wobbled away and seconds later fell to the canvas.

There would be three more knockdowns suffered by Joshua but he is adamant that the critical damage was inflicted on that first visit to the canvas. "I never recovered," he told me during a reflective interview at the English Institute of Sport.

Split seconds and fractions of inches separate success and failure across world-class sport, but in few arenas is the capacity for turnarounds as dramatic as in the ring, especially at heavyweight.

Read more from Mike Costello here.

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Luke Reddy
BBC Sport in Riyadh

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I still can’t quite believe we ended up in Saudi Arabia for this. But here we go. Costello leading Bunce and Woodhall in the desert. There’s a book about an Arabian adventure in there somewhere.

Zach Kingsbury: Joshua to use his energy conservatively and dodge Ruiz's inevitable attacks. Lord of extra weight will tire Ruiz out and AJ will end it in rounds 8-12. Let's go.

Image source, Getty Images

YouTube star KSI (and undefeated professional boxer...) is backing Anthony Joshua, by decision.

“I think there’s only two ways it’s going to go: the full 12 rounds with AJ out-boxing Ruiz and winning on points or Ruiz knocking AJ out," he said.

"AJ needs to make sure he’s focused for 12 rounds because Ruiz is very dangerous.”

Give us your predictions on #bbcboxing

Good fight, this. Alexander Povetkin has shaken off that early knock down and goes chasing Michael Hunter across the canvas before sending him tumbling.

Hunter's nose is bleeding as the bell goes for the end of the fifth round.

Luke Reddy
BBC Sport in Riyadh

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So what do we make of Anthony Joshua this week? His chats with BBC Sport’s Mike Costello have been illuminating in parts. The move to lose weight is interesting, as is the back to basics approach.

They are after all, only words.

We will find out shortly if at 16st 13lb he can hurt Andy Ruiz. We will find out if he can float under the desert sky given his trim frame. We will find out how scarred he was by being put down four times.

Just remember, if Joshua gets knocked down, he’d not be human if he wasn’t mentally transported back to New York. It is a big mental hurdle to get over should he be floored again.

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Anthony Joshua's back-to-basics approach for the bout has been well documented and he says he has no interest in delivering a "show" but is "here to win".

His promoter Eddie Hearn has expressed how nervous he is given his marquee fighter would slip down the heavyweight pecking order with a second defeat.

Joshua's trainer Rob McCracken, who faced criticism after the first loss, says his fighter is "in a much better place" this time around.

And Joshua told BBC Sport's Mike Costello defeat made him use his "time wisely" in prioritising his skills over other aspects of training.

"When Muhammad Ali was training he said he would build a shack to train in," added Joshua.

"There are clues to success and you have to go back to what it takes to be a great heavyweight champion. We had to bring in hard, rough sparring partners. I brought in the toughest and roughest."

Alexander Povetkin has already been floored by Michael Hunter, and is looking a little dazed - just the second round in that one, a long way to go...

WBA world super-middleweight champion Callum Smith: "If Ruiz wins again I wouldn't be one bit surprised. I do think you'll see a more switched-on Joshua who is more like Lennox Lewis and Wladimir Klitschko. It could be boring but I'm going Joshua late."

WBA and IBF world super-lightweight champion Josh Taylor: "I see Ruiz edging the fight just because of Joshua's past record in struggling against shorter, more compact opponents."

Give us yours using #bbcboxing

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That's what becoming a world heavyweight champion does for you...

Meeting the Mexican president, plenty of cash to splash on new motors and appearances on the Jimmy Kimmel show, Andy Ruiz Jr is enjoying his recently found fame, not that his father, Andres, is overly impressed.

"I told him 'Andy, this is your last car, don't buy any more,'" Andres Ruiz recalls.

"I said, if anything, buy a Rolls Royce and rent it out, make money. You can make $30,000 a month on it.

"Like a father, I told him to stay humble - don't spend the money, invest it in houses."

Luke Reddy
BBC Sport in Riyadh

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Welcome to the Diriyah Arena. I’m reliably informed that when Matchroom Boxing turned up here 10 weeks or so ago there was nothing here other than a flag in the ground.

Outside people filter in through security. There are ample food vans, plenty of workers telling you where to go and if all that’s not enough there’s a fairground next to the arena for the risk seeker.

I’ll be honest, I still can’t believe the first fight and I still can’t believe we’re in Saudi Arabia. Joshua v Ruiz 2 is about all the jeopardy I can handle.

Image source, Getty Images

We'll keep you up to date with what's going on in the bout between Alexander Povetkin and Michael Hunter, the penultimate fight before Joshua v Ruiz II.

Hunter has entered the ring in some fabulous headgear. He's the Predator...

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So what does Kevin Barry reckon this time around?

"Ruiz has the belts and everyone says once you become champion you're 10% better and I think that is a fair statement," says Barry.

"But I think Joshua will fight a totally different fight. When he had Ruiz down, all he had to do was take his time but he ran in with the wrong punches and put himself there to be hurt.

"This time we will see more poise. If he uses his skills and controls the pressure, I think Joshua wins the fight."