Joshua-Klitschko £40m boxing showdown embodies essence of sport

The key ingredients are in the Wembley cauldron. Now for the proof of the pudding.

The £40m heavyweight showdown between Anthony Joshua and Wladimir Klitschko in many ways embodies the essence of sport (assuming you are prepared to leave any arguments about whether boxing IS sport for another day).

The home-grown talent against the international superstar.

The bullish young pretender against the respected celebrity with a heap of trophies and scars, records and bruises to show for two decades in the spotlight, not to mention his Hollywood wife, Hayden Panettiere, and a brother, Vitali, who is Kiev mayor.

Above all, the fascination lies in the unpredictability and the timing.

If these two had met three years ago, Klitschko would have been a massive odds-on favourite. Now, the bookies lean towards Joshua.

Not all the pundits agree. Is the 27-year old Londoner, with only 18 professional fights behind him, still too inexperienced?

Or is Klitschko, an Olympic champion 21 years ago, no longer faster, higher, stronger?

His last fight suggested as much - an unforeseen defeat against Britain's Tyson Fury that ended the Ukrainian's 11-year unbeaten record.

Joshua matches his 41-year-old opponent in height (6ft 6in), and weighed in 10lbs heavier.

If Klitschko is indeed raging against the fading of the light, he is doing it with dignity and class.

As he pointed out on Thursday, the build-up has proceeded "without any f-words, punching in the face, or people throwing tables or glasses".

At Wembley, in front of a post-war British record crowd of 90,000, mutual respect and politeness will be left in the dressing rooms before the two men emerge to the booming voice of the legendary American MC Michael Buffer.

"It's a fight, right?" smiled Joshua.

The two giant US networks, HBO and Showtime, have reached an unprecedented deal to enable both to screen a fight which will be Joshua's passage to world fame and fantasy earnings - if he wins.

If he doesn't, his time may yet come.

For Klitschko, you sense, this is it.

Former world light-welterweight champion Amir Khan told me: "If Klitschko gets outboxed like Fury beat him, I think it's goodbye for him from the sport. I think it's best he retires before he gets injured quite badly."

Khan has a long-standing engagement elsewhere, but celebrity watch will be fruitful at Wembley on Saturday night, while rapper Dr Dre skyped Joshua from the US to wish him luck.

That is just the edge of the territory that beckons for Britain's 2012 Olympic champion, who still lives with his mum Yeta Odusanya in a flat in north London.

Yeta will not be at Wembley. Joshua said: "It's not a place where you want to see your kid, I don't think, at a fight."

A relative will call her afterwards to tell her whether her son is about to become one of the most famous - and richest - sportsmen on the planet.