Anthony Joshua stopped Charles Martin inside two rounds to snatch the IBF heavyweight belt off the American in only his 16th professional fight on Saturday.
With two knockdowns in the second round at the O2 Arena, Joshua secured a crushing victory that means the Olympic champion holds the leading amateur and professional heavyweight titles.
"I ain't going to get too carried away," Joshua said after stopping Martin 92 seconds into the second round.
"I've got to keep on improving. I've got David Haye calling me out, Tyson Fury calling me out."
Clean. Efficient. AJ World Champion. https://t.co/mY0huKQI6L— Adam Sweeney (@AdamWSweeney) April 9, 2016
I need to improve if I'm going to maintain and keep pushing at a higher level.
"The IBF title was previously won by Fury against Wladimir Klitschko, but the Briton was stripped of it for refusing to make an immediate defense."
I will keep on grinding," Joshua said. "Keep on working hard."
The 26-year-old Joshua is the first boxer to win the world heavyweight title while being the reigning champion in Olympic boxing's biggest weight division - super-heavyweight.
Muhammad Ali was the Olympic light-heavyweight champion when he beat Sonny Liston to become world heavyweight champion, in his 20th fight.
Almost four years after Joshua claimed gold for Britain at the London Olympics, the venue was different in the capital but there was the same raucous home support to see another dominant Joshua victory."I come to knock people out," Joshua said.
"It's about speed and precision."