The 'Special One' Kell Brook is taking a big risk when he moves up in weight to take on IBF/WBA/WBC/IBO middleweight king Gennady Golovkin on Sept. 10 in a fight matching two unbeaten champions.

Brook, who holds a piece of the welterweight title, will move up two weight classes to fight Golovkin at the 02 arena in London. The fight was negotiated quickly after talks with fellow British fighter Chris Eubank Jr. stalled this week.

Promoter Tom Loeffler,, who handles Golovkin, said Brook agreed to take the bout with the same terms Eubank was offered. It will be fought at the standard middleweight class limit of 160 pounds.

Golovkin, who has stopped his last 22 opponents, had been searching for an opponent after Canelo Alvarez decided to give up his piece of the middleweight title rather than negotiate a fight with Triple G.

Golovkin is 35-0 with 32 knockouts, while Brook is 36-0 with 25 knockouts.

Eddie Hearn of Matchroom, who promotes both Brook and Eubank Jr. - said Eubank and his father/manager Chris Eubank Sr. made the deal impossible.

"I was negotiating for three weeks on that fight and negotiating with Chris Eubank Sr. made it seem like three years. We got into a position where everybody was ready to sign, he was offered the same pay-per-view structure as Anthony Joshua, Carl Froch and the one Kell Brook accepted - but unfortunately they made the deal impossible," Hearn told Sky Sports.

"There were certain things they wanted that made it was just a complete no-go. They had deadline and they chose not to take the fight. There is a huge future for Chris Eubank Jr. He could fight the winner maybe later on in the year. He has a huge future, he misses out this time but I'm sure he'll get his shot in due course."