David Haye made a spectacular debut at heavyweight with a first-round stoppage of Tomasz Bonin at Wembley Arena.
Haye will now turn his attentions to the cruiserweight division
The 26-year-old Briton, who made his name as a cruiserweight, nailed his Polish opponent with some precise shots in the opening stages.
A combination of punches floored Bonin three times before the referee intervened to stop the fight after one minute and 45 seconds.
Haye plans to face Jean-Marc Mormeck for the world cruiserweight title next.
Haye shrugged off a weight disadvantage of a stone to improve his record to 20 wins and 18 knockouts with one loss.
My power is twice as much as a heavyweight
However, the Londoner said he had not planned to finish off Bonin so quickly.
"I was looking for a long fight and had trained for some hard rounds," said Haye. "I was looking forward to testing my defence.
"Unfortunately I let my right hand go. My power is twice as much as a heavyweight."
Haye's manager Frank Maloney said he would now begin negotiations with Frenchman Mormeck, who holds the WBC cruiserweight crown, with a view to lining up a fight before September.
"I would be mad not to take that fight and knock him out," said Haye. "I want that title."
British light heavyweight champion Peter Oboh has been stripped of his crown by the British Boxing Board of Control after refusing to defend his title on the undercard.
The 38-year-old arrived at the venue but refused to get changed to face challenger Tony Oakley, claiming he had an arm injury.
Oakey's opponent for the vacant title is now likely to be Belfast's former Commonwealth champion Brian Magee.
Maloney apologised to fans from the ring and is now aiming to stage the vacant title fight in Oakey's home city of Portsmouth.
Former world heavyweight champion Herbie Hide continued his cruiserweight comeback with a controversial stoppage of Czech Pavol Polakovic in Hamburg.
The enigmatic Norwich powerhouse forced a sixth-round victory despite labouring throughout much of the contest.
Hide, 35, won his first comeback fight last month against Valery Semishkur as he continues his bid to return to former glories.