Danny Williams smashed Mike Tyson towards retirement with an amazing fourth round knockout win in Louisville.
The 31-year-old Londoner clobbered Tyson to the canvas and straight to hospital in a fight which will rank as one of boxing's greatest upsets.
Williams withstood a terrific Tyson assault in the first round and 10 minutes later was finishing off the former world champion with a series of 26 unanswered punches.
Tyson sat crumpled against the ropes with blood leaking from his right eye until referee Dennis Alfred counted him out with nine seconds of the fourth round remaining.
And Williams capped his dream night by proposing to his long-term partner Zoe Browne.
Williams, a devout Muslim, explained: "We are already married under Islam but we are going to do it properly at register office and invite a few people.
"I was going to ask her whatever happened but after what did, I knew she would say yes."
Tyson was taken for a precautionary CAT scan and inspection of his left knee which his trainer Freddie Roach said he injured in the opening round.
Meanwhile, the unassuming Williams - given no chance by almost anybody - was preparing for stardom after gatecrashing the heavyweight elite.
Williams said: "No doubt this is the greatest feeling in the world and by far my biggest moment in boxing.
"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. I was sure I was going to win. I trained for this kind of fight. Tyson still has tremendous punching power but I saw from the Holyfield fights that if you keep throwing punches he doesn't recover all that well.
"He hurt me for a few seconds but if you've seen my fights you know I'm always at my worst in the first few rounds. The referee was a joke - it seemed like he was against me but it doesn't matter now."
Williams' final looping right hand sent Tyson to the canvas where he was left scrambling for his senses in a scene reminiscent of his shock loss to Buster Douglas in Tokyo 14 years ago.
But Roach insisted he would not immediately advise Tyson to quit and said the knee injury had hampered his progress.
Roach said: "Danny Williams surprised a lot of us and he had a good game plan and he prevailed. Right now it's hard to say what the future holds for Mike. He had a tough fight tonight and he took a lot of shots.
"I don't want to make excuses about the knee but he couldn't turn his hook over and throw it with all his power."
Williams had looked set for the quick exit widely predicted during a torrid first three minutes. He showed commendable bravery in taking the early fight to Tyson and landed a good right hand before trading in a neutral corner.
But Tyson landed a crashing four-punch combination which ended with a left hook which wobbled Williams. The Briton did brilliantly to hold on under more Tyson pressure with Tyson almost entirely reliant on crashing left uppercuts.
Williams wobbled his way back to the corner at the end of the first round but he had already exceeded many expectations. That was not enough for Williams who went on the attack early in the second and landed a superb straight left which briefly stopped Tyson in his tracks.
As the crowd roared their approval Williams then came off equal again following a frantic exchange with his back against the corner post. Williams was exceeding expectations but was deducted a point by referee Alfred early in the third following a clash which left Tyson cut over his right eye.
But after another exchange Williams was cautioned again for apparently punching low. Undaunted Williams pushed forward again and landed three clean right hands to Tyson's temple, completely unfazed by the former champion's reputation.
Tyson tried to step thins up at the start of the third with a swinging hook from either hand but his clean work diminished as both men tired through the third.
Williams stepped it up in the fourth and his camp's wild celebrations when the count reached 10 signalled the completion of what is simply a British boxing fairytale.