Minutes after heavyweight world titleholder Anthony Joshua drilled overmatched challenger Eric Molina for a blistering third-round knockout Saturday, another heavyweight came into the ring.

It was former long-reigning heavyweight world champion Wladimir Klitschko, who had been sitting ringside as perhaps the most interested spectator inside the Manchester Arena in Manchester, England. The reason was simple: An eight-figure payday and the opportunity to win back one of his old belts were at stake.

With Joshua vanquishing Molina, the Joshua-Klitschko mega fight is officially on for April 29 at Wembley Stadium in London, where a British boxing record crowd of at least 80,000 is expected. The fighters will square off for Joshua's world title as well as one of the belts vacated in September by troubled Tyson Fury, who outpointed Klitschko 13 months ago to win three major belts but twice withdrew from a rematch because of personal problems.

Although Joshua (18-0, 18 KOs) and Klitschko (64-4, 54 KOs), who are both 6-foot-6 and 245 pounds, will appear at a news conference at the Stadium on Wednesday, they kicked off their promotion inside the ring for the bout that will headline a Sky Box Office pay-per-view card in the United Kingdom. American television rights are still up for grabs, with Showtime and HBO locked in a bidding war, a network source told ESPN on Monday.

Wladimir Klitschko on squaring off against heavyweight world titleholder Anthony Joshua on April 29: "I'm looking forward to this fight of the year, just like boxing fans all around the world." JOHN MACDOUGALL/AFP/Getty Images

Klitschko, a 1996 Olympic gold medallist, and Joshua, who won Olympic gold in 2012, have tremendous respect for each other, dating to when Joshua was a rising prospect and spent time in one of Klitschko's training camps as a sparring partner when he was getting ready for a title defense. Klitschko praised his game and work ethic back then and did so again as the fight was made official.

"He is the best man in the heavyweight division, and his record speaks for itself," Klitschko said. "This is the fight that the fans want, and that is why this fight will happen. Do you want to see a big fight? Do you want to see a fight where two Olympic champs are involved? Do you want to see the fight between A.J. and W.K.? You got it."

Said Joshua, standing next to Klitschko: "He's a very respectful man outside of the ring, and he's very competitive in the ring. This is the step up people have wanted. Klitschko wants his belts back, and may the best man win."

Joshua promoter Eddie Hearn and Bernd Boente, Klitschko's manager, tried to make the fight this month, but for various reasons, they elected to delay it until the spring, mainly so as not to rush the promotion for such a huge event. Instead, Joshua faced Molina with the Klitschko match contingent upon a win.

"I'm so happy to get this fight made," Hearn said. "It is the biggest heavyweight fight in the last decade and a fight that will belong in the legacies of both fighters. It's the young lion against a legend of the sport.

"Many felt AJ would not take this challenge and that it's too early for him, but he wants to test himself and give the fans great fights. After all, isn't that what you want to see? The risk, the dice being rolled, the 50-50 fights that will excite and ignite the world of boxing. Everything is on the line in this fight -- not just the IBF and WBA's titles, but hopes, dreams and even careers."

Said Boente: "I'm very happy that our teams [made] this mega event happen. Two Olympic super heavyweight champions facing each other. This is the best heavyweight fight that could be made. This is a promoter's dream fight: the young, undefeated champion against the best heavyweight of the past decade. This kind of duel [has] only happened a couple of times in boxing history, and it was always the same question: Is the young lion ready to take over, or can the old lion defend his territory?"

Klitschko, who will turn 41 a month before the fight, will be boxing for the first time since a loss to Fury and will be entering the ring in an unfamiliar position -- as challenger -- after reigning as champion for nine-and-a-half years (second-longest in heavyweight history) and making 18 title defenses (third-most in division history). He will be appearing in his 29th world heavyweight title fight, which will extend his division record.

"I'm looking forward to this fight of the year, just like boxing fans all around the world," Klitschko said. "This is the first time in a decade that I'm the challenger again. I will fight against a champion who I consider the best of the young generation. Basically, experience will take on youth. This makes this fight that unique. I will be ready for the challenge."

Joshua, 27, has looked superb so far as a professional and has been dominant in his title bouts, dusting Charles Martin in two rounds to win the belt in April, dominating Dominic Breazeale en route to a seventh-round knockout in June and blowing away Molina. Klitschko, however, is in a different league than all of them, and Joshua knows it.

"This fight will be one of the biggest nights in my boxing career," Joshua said. "It marks the highest point of my climb through the professional ranks. It is three years since I turned professional. I have taken the time to gain experience, fight men who have fallen and some who have fought hard, and through this, I am learning my trade, how the business works and gaining the ring craft, which is sometimes underestimated, as everyone wants to see the mega fights right away.

"It is the perfect time for me to move up another step and contest my heavyweight championship belt against one of the legends of our sport. There is no doubt this will be a titanic battle with a huge amount on the line, just like every fight. But when I enter the ring, I will be prepared for victory, as I have been with all my other fights. The legend against the champ -- it's time to write history."