Kell Brook lands a punch on Shawn Porter during their welterweight title fight in August 2014 at StubHub Center/AP file photo by Chris Carlson

Kell Brook holds one of the welterweight title belts, but he is a big welterweight and he believes there will be no weight advantage for Gennady Golovkin when the two square off Sept. 10 for Golovkin’s middleweight titles at O2 Arena in London (on HBO).

The interested parties gathered Monday at a news conference in London. Brook made sure everyone knew he won’t be the smaller man in the ring come fight time.

“This is the biggest fight in world boxing,” said Brook, of England. “I’m the best welterweight in the world and no-one wants me, he’s the best middleweight in the world and no one wants him. I’ll be his size on fight night and I’m bringing the speed to middleweight.”

According to one source who requested anonymity, Brook was walking around at 178 pounds at the July 14 news conference in New York City promoting this fight. And he was not fat. The welterweight limit is 147, middleweight is 160.

Golovkin spoke as if he knows he won’t have a cake walk.

“Kell Brook has my full respect and a great team behind him,” Golovkin said. “It’s not easy for us to get opponents. He’s ready for me and I’m ready for him. Kell Brook is the biggest test to me. He’s a great champion, he’s moving up in weight, but great fighters have done that and I know he’s a great boxer and he will test me the most.”