LONDON -- To see middleweight titleholder Gennady Golovkin and welterweight titlist Kell Brook stand face to face to pose for photos -- and then shake hands like the true pros that they are -- following Thursday's final news conference one would never guess that Brook is coming up two weight divisions to challenge the most feared man in boxing.
They look roughly the same size, but that is just what Brook is going to do when they meet in a fight with potentially historic implications on Saturday (HBO, 5:30 p.m. ET/PT with a replay at 10 p.m. ET/PT) at the sold-out O2 Arena.
Brook (36-0, 25 KOs), 30, who will have his home country behind him, admittedly has struggled to make the welterweight limit of 147 pounds in recent fights, but he has done it. He has defended his world title three times, all by knockout, since traveling to the United States and upsetting Shawn Porter to claim the belt by majority decision in August 2014.
"This fight couldn't have come at a better time for Kell. He's been looking to move up in weight for a long, long time but we pursued the route to the welterweight title," trainer Dominic Ingle said. "But we had 20-week training camps just to get down to weight. There's been times we had him on special diets so he could safely make the weight. People are now realizing that Kell Brook is not a small guy, a welterweight stepping up to challenge a middleweight.
"This is the only time I've seen him happy in a training camp. Never had a smile on his face when he had to make 147, but this time he's been happy the whole training camp as he makes 160."
Indeed, at various mandated weight checks, Brook outweighed Golovkin each time and looks strong at his new weight.
He wanted to face top names in the loaded welterweight division, just like Golovkin has wanted to at middleweight, but neither could get any takers. When Brook's promoter, Eddie Hearn of Matchroom Boxing, offered him Golovkin -- when Golovkin's fight with contender Chris Eubank Jr. went south -- Brook immediately accepted. He is that confident in himself.
"I am happy with the decision to make this enormous fight, and the sold-out crowd and the viewing figures on TV will prove that this is a massive fight," Brook said. "Everyone in boxing knows that I am a big guy. People who don't know think that the weight is going to be an issue. I'm more vicious in sparring when I am around 160 pounds or coming down from heavier than that. That's where I am healthier in training and I can give so much more output in the gym, and that means the full 100 percent will come from me in the fight.
"I believe [the result is] written and I will shock the world Saturday night."
He and Hearn believe a win would be the biggest in British boxing history. If some disagree there is no question it would at least be in the conversation along with fights such as Randy Turpin's 15-round decision upset of Sugar Ray Robinson to win the middleweight title in 1951, Ricky Hatton's 11th-round knockout of Kostya Tszyu to win the junior welterweight title in 2005 and Tyson Fury's decision win over Wladimir Klitschko 10 months ago to win the heavyweight title.
"People who don't know think that the weight is going to be an issue. I'm more vicious in sparring when I am around 160 pounds or coming down from heavier than that... I believe (the result is) written and I will shock the world Saturday night." Kell Brook
"Kell is moving up two weight divisions to fight the most feared fighter in world boxing," Hearn said. "There have been some huge British wins, but as a one-off win I think this is up there with one of the greatest wins of all time. Brook beating GGG is on another level because you're fighting a top pound-for-pound fighter in his prime. If Hatton would have beaten Floyd Mayweather that possibly would have been the greatest win for a British fighter, but he didn't."
Said Brook: "I have to say that me winning this fight Saturday night is the biggest win in British history of any era. Me moving up two weight divisions to beat the most feared man on the planet, unified middleweight champion, is the biggest win. Sugar Ray Robinson is my favorite fighter of all time and Turpin's win is way up there but you have to put this one off win I will get as the best ever in British history."
K2 Promotions' Tom Loeffler, who represents Golovkin, has had a bear of time making matches for GGG and was relieved when Brook accepted the fight.
"We don't have to go through the list of all the full fledged middleweights who have turned down fights, given up titles and negotiated until the 11th hour and then not sign the contract," Loeffler said, referring to opponents such as Canelo Alvarez, Billy Joe Saunders and Eubank. "It's unbelievable how difficult it was to find someone to get in the ring with Gennady."
But Brook agreed and if he pulls off the upset -- he is a considerable underdog -- he will become only the third reigning welterweight titleholder to move up and win a middleweight world title. The others are all-time greats enshrined in the International Boxing Hall of Fame: Sugar Ray Robinson and Carmen Basilio, both of whom did it in the 1950s.
"I'm going to follow the greats and make history," Brook said. "The likes of Felix Trinidad, Sugar Ray Robinson, Sugar Ray Leonard, Floyd Mayweather, Manny Pacquiao have all moved through the weights to prove they are greats at all weights. There's a small window of opportunity to do something special and I am going to take my chance to prove that I am a special fighter.
"The fans pay our wages and I want to give back to the fans. I have been telling them for ages that I want big fights and they haven't believed me. They don't know the politics that go on behind the scenes through no fault of my own. I've had injuries, mandatories. It's been hard to get big fights, and as soon as there's been the window of these big fights happening, I've been let down by people not wanting to dance."
"I respect Kell Brook and his team. I know he understands for both of us, this is the biggest fight. He looks ready, I'm ready. This is a big gift for boxing fans. Not just in the U.K., but for all boxing fans." Gennady Golovkin
Brook's countryman, Amir Khan, whom he has verbally sparred with for years but never been able to finalize a fight with after multiple attempts, moved up from welterweight to middleweight (albeit at a catch weight) to face lineal champion Alvarez in May but got badly knocked out in the sixth round. Brook does not plan on that happening to him.
His moniker throughout his career is "The Special One," and now he wants to prove it against no ordinary titleholder. Golovkin (35-0, 32 KOs), 34, the Kazakhstan native fighting out of Santa Monica, California, will be making his 17th title defense. He has knocked out 22 opponents in a row, his knockout percentage of 91.4 is the highest in middleweight title history and he has displayed an iron chin.
Yet, Golovkin has shown enormous respect for Brook and sure made it sounds like he presents at least some danger.
"I respect Kell Brook and his team," Golovkin said. "I know he understands for both of us, this is the biggest fight. He looks ready, I'm ready. This is a big gift for boxing fans. Not just in the U.K., but for all boxing fans.
"Kell Brook is a very good boxer and I respect him for taking this fight. He is more than ready. He is an undefeated champion and this will be the biggest fight of my career. He is coming up from welterweight so his speed will be a new test for me. I hope our styles match well to give the fans a present. I want to produce a dramatic show and that is why I have come to London."
Brook, however, did not sound like a man preparing to rely on speed. He has quite a bit of thunder in his fists and believes the power will join him in his new weight class.
"When he feels the power that I have that's going to be a strong, powerful and quick middleweight hitting him, not a welterweight," Brook said. "I'm going to put it all together. Golovkin is like Mike Tyson -- people have lost before they even get in there with him. I'm not interested in what he's going to do. I'm focused on what I need to deliver to win."
Hearn said he was surprised by the overwhelming response from the public when the bout was announced. "This fight has hit fever pitch -- fans coming up to me dozens of times today and asking, 'Can Kell do it? He looks strong. Is GGG really the beast people say he is,'" Hearn said.
And then Hearn, who needed barely a couple of days to finalize the fight with Loeffler, took a whack at those who fled from sharing a ring with Golovkin.
"Any fighter who wishes to face Gennady, these are very easy people to deal with," Hearn said. "They just want to fight the very best and that's what they are doing with Kell Brook, 35-0 versus 36-0. It doesn't get any bigger or better than this."
Hearn, who has a close relationship with Brook, was pleased to be able to deliver such a huge fight to him.
"There are so many times I've sat with him and his dad and they said, 'We want it all, we can beat them all. You just have to give us the chance to show it,'" Hearn said. "On Saturday, he takes the outrageous leap of two weight divisions to a place where he knows he is so comfortable, so much stronger, so much more full of belief. But in front of him he has the toughest, most dangerous fighter in world boxing. But isn't that what the sport is about? Isn't it about the best fighting the best?
"Two undefeated fighters, two fighters with so much talent, so much skill, so much power, so much grace, in front of 17,000 people, an event that sold out in only  minutes. This is what the sport is all about."
That, and possible history for Brook, who can truly earn his "Special One" nickname with a victory.