-- Unified middleweight titleholder Gennady Golovkin will defend his belts against welterweight world titlist Kell Brook on Sept. 10 at the O2 Arena in London, organizers announced Friday in a huge surprise.
The match comes as a shock because Golovkin promoter Tom Loeffler of K2 Promotions was close to finalizing a deal with Matchroom Boxing promoter Eddie Hearn for Golovkin to defend against middleweight contender Chris Eubank Jr.
Hearn was also in the process of finalizing a deal with Top Rank for a welterweight unification fight between Brook and Jessie Vargas.
But Eubank seemingly got cold feet when it came to fighting Golovkin. The Brook-Vargas deal, meanwhile, became difficult to finalize because, according to Top Rank, Hearn wanted to reduce the money he was going to pay Top Rank by 20 percent after the recent steep devaluation of the British pound.
So voila: Golovkin-Brook became a reality. Already blown off for a fall fight by lineal middleweight champion Canelo Alvarez, as well as titleholder Billy Joe Saunders and now Eubank, Golovkin needed an opponent.
And Brook, looking at taking a smaller share of the money against Vargas, instead elected to go for the bigger fight against Golovkin and agreed to move up to 160 pounds. There is no catchweight for this bout.
"I cannot tell you how excited I am for this megafight," Hearn said. "I've worked hard with Tom over the years to bring GGG to the U.K. Right here you have the No. 1 welterweight in the world against the No. 1 middleweight in the world -- 36-0 versus 35-0, two of the best on the planet. It's what big-time boxing is all about."
Golovkin-Brook will air in the United States on HBO and on Sky Box Office pay-per-view in the United Kingdom.
"I'm very excited to be fighting in front of the great British boxing fans and promise another big drama show against Kell Brook," the 34-year-old Golovkin said.
Golovkin (35-0, 32 KOs) is coming off a crushing second-round knockout of mandatory challenger Dominic Wade on April 23 at the sold-out Forum in Inglewood, California. He has defended his title 16 times -- closing in on Bernard Hopkins' division record of 20.
Golovkin, of Kazakhstan, has also scored 22 knockouts in a row, owns the best knockout percentage in middleweight title history (.914) and has not gone the distance since winning an eight-round decision in 2008.
None of those gaudy statistics discouraged Brook, who has said time and again that he wanted a big fight. Now he has one.
"This is the fight and the moment I have been waiting for for some time," Brook said. "We've tried and tried to lure the best to come and fight me, and now we've got the best of the best. The No. 1 pound-for-pound fighter in the world is coming to the U.K. When this fight got offered to me, I accepted within minutes, and I can't wait."
Loeffler said finalizing the bout was a snap.
"Everything was great with the Eubank fight, and Eddie was very confident he could close a deal with him. As it started getting into the finer points of the deal he was running into issues with Eubank. By Wednesday he told me he had hit so many roadblocks that he wasn't confident it would happen," Loeffler told ESPN.com.
"So he said to me, 'Let me see if Kell Brook would take the fight under the same conditions.' And he called me back about two hours later and said Brook will take the fight. He said he offered Kell the same deal he offered Eubank and Kell jumped at it. It took us a day to finalize the agreement and we announced it [Friday].
"Kell said after his last fight that he wanted to fight Gennady, but I didn't think that was realistic. Eddie said it was back then, and that's what gave him the idea to offer it to him for Sept. 10."
Brook (36-0, 25 KOs), 30, of England, traveled to the United States and outpointed Shawn Porter to win a welterweight world title in August 2014. He has made three defenses against lesser opponents since -- knockouts of Jo Jo Dan, Frankie Gavin and Kevin Bizier. All the while he was calling for a big fight.
Brook will be moving from 147 pounds to 160 to face Golovkin after a similar move by rival countryman Amir Khan, whom he has not been able to make a deal to fight despite massive public interest in the United Kingdom. On May 2, Khan, a former junior welterweight titlist moved up from welterweight to a 155-pound catchweight to challenge Alvarez for the lineal title and got knocked out in brutal fashion in the sixth round in Las Vegas.
Brook said moving up two weight divisions won't be an issue for him against GGG. Even if he loses, he would still have a welterweight title and could return to the division to defend it.
"Everyone knows I'm a huge welterweight, and I know I will carry my speed and accuracy and even more power through the weights," Brook said. "This is the ultimate fight, one of the biggest international fights the country has seen in many years. You have seen some huge names run from GGG, but I'm running to him. I'm a special fighter and I will show the world on Sept. 10."
Loeffler said he commended Brook for his willingness to tangle with an opponent so many have avoided.
"Kell is coming up in weight, but Gennady is going to Kell's country. Kell is the one who finally stepped up to fight Gennady," Loeffler said. "We tried to make Carl Froch [at super middleweight a couple of years ago]; we reached out to Billy Joe Saunders to unify. We said we would go to England to fight and him and he would have gotten his biggest purse, but he wouldn't take the fight. Then we went through this exercise with Eubank and now we're here with Kell Brook.
"We have an undefeated welterweight champion and the best welterweight in the world willing to move up to face the best middleweight in the world, and the best middleweight in the world is willing to go to Kell Brook's country to defend all of his belts. They both had the same problem. Kell Brook could not get the big welterweight names to fight him like we could not get the big middleweight names to fight Gennady. This solves the problem for both fighters and creates and massive event."
Said Hearn: "I couldn't be happier for Kell. We have pushed for that big name for a long time with many reluctant to step into the ring with him, and now this is the ultimate challenge, the biggest fight of 2016, and I can't tell you how happy I am to bring it to the U.K. Sept. 10 is going to be an incredible night at the O2. It's a special night for British sport and we will provide a packed show with multiple world title fights and some of the biggest names in British boxing."