Danny Williams caused one of the biggest upsets in boxing history with a fourth-round knockout of Mike Tyson in their heavyweight fight in Louisville.
The Englishman had looked in trouble early on against the powerful American, taking a couple of heavy punches.
But Williams weathered the storm and when he started to attack, the former world champion had no answer.
Tyson was knocked down towards the end of the fourth round in what could signal the end of his career.
It was only the fifth time the 38-year-old had been beaten.
Meanwhile Williams, who was 9-1 outsider and largely written off as a no-hoper before the fight, will now feel he has a shot at a world title fight.
"This is the greatest feeling in the world and by far
my biggest moment in boxing," said Williams.
"I said I would get him after the fourth round but we didn't quite make it that far.
"I proved people wrong - they have to take me seriously now."
Tyson came out firing in the opening round, tearing into his unfancied opponent.
And it soon became one-way traffic with the Londoner clearly shaken after a crunching four-punch combination from the 38-year-old.
But the 31-year-old Briton did brilliantly to hold on under more pressure with Tyson almost entirely reliant on crashing left-hand uppercuts.
Williams went on the attack early in the second and landed a superb left which briefly stopped Tyson in his tracks.
But in the third he was unluckily deducted two points by referee Dennis Alfred, first for a clash which left Tyson cut and then for a low blow.
Williams, however, pushed forward again and landed three clean right hands to Tyson's temple.
The American tried to step things up at the start of the fourth, but when Williams landed 26 unanswered blows, the self-proclaimed "baddest man on the planet" crumbled against the ropes for the fifth defeat of his tempestuous career.
Tyson left the ring refusing to talk, but his manager
Shelly Finkel blamed the defeat on a twisted knee late in the first round.
"He couldn't get leverage," Finkel said. "When the guy
was leaning on him I knew it would be a bad night."