Gennady Golovkin retained his WBC and IBF middleweight titles after overcoming Kell Brook's stunningly daring high-wire act in five remarkable rounds at the O2 Arena.
Brook, who remains the IBF welterweight champion despite going down to a first career loss, stepped up two divisions to face the sport's most fearsome operator in Golovkin.
The 34-year-old Kazakh, now in possession of a remarkable record of 36 wins from 36 fights and 33 inside the distance, eventually stalked and pounded Brook to a standstill in round five as the Sheffield fighter's corner frantically waved a white towel.
Speaking after the fight, Brook said he believed Golovkin broke his eye socket during a barnstorming second round and his bloodied features told their own story when the end came after one minute and 57 seconds of the fifth.
The right hook followed by a left uppercut landed flush. Golovkin absorbed them with little complaint as the volume in the arena cranked up a few more gears.
Brook joined Golovkin in calling for a fight with Alvarez afterwards. He will have to get into line behind the sport's leading light, but thanks to Ingle's selfless act, his time to impress on the biggest stage will come again.
"I expected him to be a bigger puncher," Brook said. "In the second round he broke my eye socket but I was tricking him, I was frustrating him. I was starting to settle into it but when you see three, four, five of them it's difficult.
"I hurt him. When you're in the fight you can see, his legs buckled a little. ... I would fight him again, with a good eye."
Indeed, Brook's trainer, Dominic Ingle, was jeered by the capacity arena crowd after throwing in the towel.
"You can't be fighting a guy like Golovkin when you can't even focus on the guy," promote Eddie Hearn said, referring to Brook's eye injury.
