David Haye had Monte Barrett down four times before the fifth-round knockout
David Haye announced his arrival in the heavyweight division with a stunning fifth-round knockout of Monte Barrett.
The Briton, fighting for the first time since moving up from cruiserweight, had his American rival on the canvas four times before finishing the job.
The Londoner was knocked down himself at the start of round five before a lethal combination ended the fight.
Haye now hopes to challenge either Wladimir or Vitali Klitschko for one of their world titles early next year.
Vitali was ringside to watch Haye demolish veteran Barrett, and the manner of the victory would have given the Ukrainian food for thought ahead of a possible fight next year.
Haye, who now holds a record of 22-1 (21 KO), was delighted with his win, insisting Barrett has been a dangerous opponent.
"Heís a quick heavyweight, but my speed told," said Haye. "He definitely came to win and put me down with a good shot.
"I expected to get knocked down and I did. Thatís what youíre going to get with me in the heavyweight division. I might get down but Iíll get back up and Iíll do what I have to do.
"I wasnít out of breath, my power felt great. Without having to boil down the make weight, every shot I threw felt harder than ever and I felt faster than I did at cruiserweight."
But Haye admitted Barrett had given him a few pointers about life in the heavyweight division.
"His shots felt a lot harder," said the Englishman. "Even his jab was the equivalent of a cruiserweightís right hand, and thatís something Iíve got to get comfortable with."
Haye's trainer said there was plenty for his man to work on.
Get into slugging matches and heíll lose his sharpness, David has to use his feet
"He didnít stick to his game-plan," said Adam Booth. "Monte managed to draw him into a slugging match. Get into slugging matches and heíll lose his sharpness, David has to use his feet.
"All fighters have to stand and trade at times, but the fewer times you do it, the better it is for your health."
Barrett looked nervous before the fight had even begun, tripping on his way into the ring, while Haye looked composed and calm despite stepping into the relative unknown.
Haye had not fought since demolishing Welsh cruiserweight Enzo Maccarinelli inside two rounds in March, while the last time he fought at heavyweight was in 2007.
But the 28-year-old imposed himself on the fight from the first bell, catching Barrett with a fine left hook.
Two right jabs before the end of the round tested the chin of the American again.
The second round was relatively quiet, with neither boxer landing clean shots, but the fight exploded into life in the third.
Haye, whose hand speed was starting to test Barrett, floored his 37-year-old rival with a thunderous left hook.
Barrett climbed off the canvas but was again floored, this time with a right, but again he beat the count. As Haye went in to finish the job, the American was saved by the bell.
Haye was knocked down at the start of round five
The fourth round was almost a carbon copy of the third, with Haye knocking down Barrett again with a decent left hook.
Soon after, a right uppercut looked to have finished the fight only for the bell to come to his opponent's rescue again.
There was controversy at the start of the fifth round when Haye was hit while on the floor after being knocked down himself.
An increasingly reckless and desperate Barrett was deducted a point following the incident.
But the contest was soon over as Haye put together a lethal right-left combination that floored Barrett for the fifth and final time.
Referee Richie Davies began the count but gave up at three, waving the fight off much to the delight of the crowd at the O2 Arena.
On the undercard, British light-middleweight champion Ryan Rhodes beat South African Vincent Vuma to take the WBC International title.
The 31-year-old from Sheffield won the fight convincingly with scores of 117-111, 116-112 and 116-113 in his favour as he moves closer to a WBC world title shot.