By Ben Dirs
BBC Sport at the O2 Arena
David Haye will now try to dominate the heavyweight division
David Haye stopped Enzo Maccarinelli in the second round at London's O2 Arena to add the WBO cruiserweight title to his WBC and WBA belts.
The bout failed to live up to the hype, with a cagey opening round followed by an explosive second, Haye flooring Maccarinelli with a huge right hand.
Maccarinelli rose early but was backed into a corner by Haye before referee John Keane decided to halt the contest.
Afterwards, Haye, 27, said he intends to step up to the heavyweight division.
"A lot of people said Enzo could beat me, so this is what had to happen before I moved up to heavyweight and became the undisputed heavyweight champion of the world," said South London's Haye, who now has 21 wins (20 KOs) and one defeat.
"There'll be just as many people doubting me as there were doubting me before this fight, saying I'm too small, I've got no chin, no stamina.
"But I'm 100% certain that I'll achieve more things at heavyweight than I have done at cruiserweight.
If I've got to go to Russia or to Vegas, I'll go there. As long as there's a ring and a referee who can count to 10, I'm sorted
"I'd fight [IBF and WBO heavyweight champion] Wladimir Klitschko in my next fight if I could after his pitiful fight against Sultan Ibragimov.
"That was embarrassing and he wouldn't look forward to fighting someone with my kind of style - powerful, explosive and able to take him out with any shot.
"I'll work my way up the rankings, I'm not looking at taking shortcuts, and you guys will get a real entertaining ride.
"I'm not looking at boxing into my 31st year, so I've got two and a half years to get the job done. If the titles get unified, hopefully I'll just have to fight one guy."
Haye and Maccarinelli finally entered the ring at approximately 0215 GMT for the benefit of an American audience.
The crowd of 20,000 had been kept awake by a fine domestic super-featherweight clash between Kevin Mitchell and Carl Johanneson, which Mitchell won impressively.
Haye looked in sensational shape and fully focused before the opening bell, while Maccarinelli, accompanied to the ring by gym-mate and super-middleweight king Joe Calzaghe, showed signs of nerves.
Almost inevitably following months of promotional hoopla, the opening three minutes were a cautious affair, although Maccarinelli did appear to wobble Haye with almost his first punch, a flashing left hook.
However, Maccarinelli stood off, allowing Haye to compose himself and hit back with a couple of big lefts of his own and a hurtful overhand right.
Haye landed another booming right early in the second before Maccarinelli opened up a cut over Haye's left eye with another flashing left.
However, Haye, feeling blood trickling down his face, stepped up a gear, bundled Maccarinelli into the corner and sent home a savage right that left Maccarinelli sagging on the ropes.
Maccarinelli rose early and reeled backwards on unsteady legs before being allowed to continue, only for Haye to clip him with another big right hand.
With Haye moving in for the kill, referee Keane called a halt after two minutes and four seconds of the round.
Haye shows his delight after beating Maccarinelli
Haye said of the stoppage: "Once I realised I was cut I had to take a couple of risks. As soon as I felt the blood, Adam [Booth, his trainer] said close the show, so I did."
Swansea's Maccarinelli, who slipped to 28 wins (21 KOs) and two losses, said he had failed to execute his pre-fight plan.
"I made a mistake, simple as. I caught him in the first round with a short left hook but I didn't jump in and do what I should have done and in the second round I put my chin up in the air and he caught me, jumped in and finished me off," he said.
"I should have taken a knee, but I didn't and he jumped in and showed he's a good finisher.
"Everyone knew he was a banger and everyone knew it was going to go early and it was a case of who landed first. I landed in the first round and didn't capitalise, he capitalised, end of story and all the best to him.
"He was a lot faster and a lot sharper than I thought he would be. He does hit hard and he's got all the attributes to go up to heavyweight."
Haye added: "It was all about putting on a good show for an American audience because they really crave an exciting heavyweight who is not scared to put it on the line and hopefully they realise that's me.
"If I've got to go to Russia or to Vegas, I'll go there. As long as there's a ring and a referee who can count to 10, I'm sorted."