Anthony Joshua v Wladimir Klitschko: Is Briton the perfect heavyweight?

A crowd of 90,000 around the ring at Wembley, a million more on pay-per-view at home, an opponent who has been in more world title fights than he has professional bouts.

Little about Saturday's heavyweight showdown with Wladimir Klitschko should leave Anthony Joshua as unnaturally calm as he appears to be. But the kid from Watford turned IBF world champion stands in a sweet eddy in his division's turbulent waters - the past all promise, the future more auspicious still.

Heavyweight boxing is so often about hope and hype above authenticity, delusion rather than cold reality.

Punters come back not because so many title fights prove unforgettable, but for the promise that the next really will be - repeat experiences of disappointing champions, meaningless titles and badly made matches pushed away by the beguiling possibility of what might yet lie ahead.

Joshua - 18 fights and less than a cumulative two ring hours into a professional career that followed hard on a late start and rapid progression - goes to Wembley defined by the same heady mix of promise and possibility: that at 27 he has too much speed and power for the 41-year-old Klitschko, that his rapid improvement will continue at the same steep pace, that he could yet prove the perfect heavyweight at an imperfect time for the most captivating class of all.

For the Joshua of today - hours before the biggest test of his sporting life - appears to have everything the archetypal champion should possess.

• Ali? Lewis? Klitschko? Which heavyweight great are you?

• Klitschko fight a whole new level - Joshua

• Joshua v Klitschko preview - BBC Radio 5 live podcast

Gold in London 2012: The judges scored the super-heavyweight final with Italy's Roberto Cammarelle 18-18 with Joshua winning on countback

There is his physique: big without being bulky, powerful but explosive, a little reminiscent of Ken Norton through his mid-70s trilogy with Muhammad Ali.

There is the back story: just the right amount of jeopardy, on remand in Reading prison and later caught in possession of eight ounces of cannabis, before a classical conversion to boxing via a dedicated cousin and grassroots coach, winning the last home gold medal of Great Britain's historic haul on the very last day of the 2012 Olympics.

There is the unpretentiousness of a man who still lives much of the time with his mother, Yeta, in Golders Green, north London. He has prepared for Saturday night with a three-month training camp at the same unglamorous English Institute of Sport in Sheffield that was both home to fellow Olympic champion Dame Jess Ennis-Hill and where he trained under coach Rob McCracken in the build-up to those London Games.

There is enough easy charisma to attract both boxing acolytes and cynics, enough charm to stop for every selfie without making it look like a conscious exercise in personal marketing, sufficient understanding of where he has come from to recently gift that first coach at the Finchley & District Amateur Boxing Club, Sean Murphy, a brand new BMW with personalised plates.

And there are the knockouts. Eighteen in 18 pro fights, 13 of them inside the first three rounds.

People don't pay big money for heavyweight fights to see them go the distance. Nobody turned up to watch Mike Tyson look technically neat for 12 rounds. Lots have decried Klitschko for his sensible strategies.

They go to see it end as quickly as possible, the sudden termination worth more than a drawn-out dance. It is the only sport where punters are more satisfied the less they see.

As Joshua said when bumping into a beaming Jose Mourinho backstage at the O2 arena a year ago after taking the IBF heavyweight title from Charles Martin with a second-round knockout: "People want to see blood, uh?"

That was the first fight Mourinho had ever been to - another illustration of Joshua's rare draw, with the Manchester United manager's star-struck grin one more. Joshua looked as relaxed as if he was shaking hands with a steward, his composure as unbroken as it had been in the ring.

All possibilities, all promises. All pointers to a special future and a place amongst the elite.

And yet so little of it can be guaranteed this early in his entry into a brutal business, not when the challenges will keep coming in different shapes and guises both on Saturday and beyond.

• Klitschko bout perfect time for Joshua - Lewis

• 'Father Time has caught up with Klitschko'

Delivering the knockout blow against Eric Molina to successfully defend his IBF heavyweight title in 2016

There is no obvious nastiness about Joshua, his behaviour in the build-up to this fight is in contrast to that of fellow Britons David Haye and Tyson Fury in their own battles with Klitschko. In traditional boxing parlance that is a flaw rather than a strength. Villains sell tickets. Bad guys get paid to be bad.

When you've sold 90,000 tickets on the appeal of your other attributes that may be less of a worry than it would be for other fighters.

But there are still great unknowns amid the allure. How might a man who didn't box until after his 18th birthday fare against an opponent who has been fighting in front of stadium sellouts for decades? How will a kid who was seven years old when Klitschko made his professional debut cope with an atmosphere that British boxing has never seen before?

Age gap: Klitschko on his way to winning gold at the 1996 Atlanta Olympics - when Joshua was only six years old

Klitschko is now 41 years old. He was soundly beaten by Fury and hasn't fought in the 16 months since. But he has held all three world titles and lost only four out of 68 professional fights.

When Joshua last felt real pressure - in his grudge match against Dillian Whyte - the composure sometimes slipped. In his rush to finish it, he was almost finished himself.

"There is a chance that Josh could be completely out of his depth," says his promoter Eddie Hearn, before adding: "And there is a chance he could be the fighter we believe he is, and he goes out there and dismantles Klitschko. No-one really knows - and that's the beauty of the fight."

Can Joshua handle the unexpected explosive punch? Maybe very few heavyweights can. Ask Lennox Lewis about that night in Carnival City Casino and the impact of Hasim Rahman's right hand.

Maybe the rumours of Joshua being dropped in sparring are just that, or that he is not a gym fighter, or that he needs the challenge of a big fight to bring out his best. Maybe it doesn't matter that only twice in his professional career has he gone beyond the third round.

"Professional fighters - we're not gods, we're not superheroes," he has said. "We are just human and we make mistakes."

Are greater fame and fortune on the cards for Joshua with a win over Klitschko?

At this moment, Joshua has both a burgeoning aura of invincibility and the character outside the ring to match it. He is also at his tipping point between relative fame inside sport and a leap - should he triumph at Wembley - into the wider public consciousness.

"If it's all fake, people will soon figure it out," he has said. "Just be yourself."

The one-time bricklayer believes it. He also admitted recently that he is aiming to become boxing's first billionaire. Both that and the extravagance of his recent escapades on holiday in Dubai pointed to a possible contradiction between the two positions. Few intend to change when they pass through that tipping point - but when the world around you changes, you tend to adjust to it.

It is all part of the fascination with Joshua, all part of that same magic blend of prospect and probability.

Nothing has been lost, everything is still possible. Boxing still feels fresh to him, its fascination bright, his love of its nuances and enthusiasm for its punishing routines undimmed.

And so we wait, hoping again, drawn in once more by rich promise and real talent - and, of course, a little hype.

Get all the latest boxing news leading up to the Joshua-Klitschko fight, sent straight to your device with notifications in the BBC Sport app. Find out more here.