England's Danny Williams admitted he could barely believe he had beaten former world champion Mike Tyson after his surprise victory in Kentucky.
The unfancied Williams knocked Tyson out in the fourth with a flurry of punches to produce one of the greatest upsets in recent boxing history.
"It feels unbelievable to have beaten a guy I've watched for years," Williams told BBC Five Live.
"The greatest thing of all is that I won when no-one gave me a chance."
Williams marked the occasion of the most famous win of his career by proposing to long-term girlfriend Zoe Browne in the ring.
She accepted without hesitation to cap the perfect night for Williams.
He credited his victory to his superior fitness, with the 38-year-old Tyson appearing to run out of steam after a bright opening.
"I was told that it would get easier and easier as the rounds went by and that was the case," he said.
"He was hitting me and it didn't seem to hurt as much as the previous round so I knew I was getting to him and that he was getting tired.
"I knew I was going to stop him because my conditioning was far better than his.
"In the first round I was hurt for about 15 seconds after he caught me with a good shot but I held on, gritted my teeth and gave it back to him."
The 31-year-old said he was surprised by Tyson's mental approach to the fight.
"It's not really my thing to stare at people but (before the fight) he wouldn't look at me, so I wanted to stare at him to frighten him," said Williams.
"Even at the weigh-in he wouldn't look me in the eye. I don't know if he was wary of me, or just wary because he'd been out of the ring for so long, but he wasn't that confident in himself."
DANNY WILLIAMS FACTFILE
Born: 13 July 1973 in Brixton
1995: Turns professional, winning first fight against Vance Idiens
1998: Wins vacant WBO Inter-continental heavyweight title against Antoine Palatis
1999: Loses fight for British and Commonwealth heavyweight title to Julius Francis
2000: Dislocates shoulder but recovers to beat Mark Potter for the British heavyweight title
2003: Knocked down three times in losing European heavyweight title bout to Sinan Samil Sam.
2004: February - loses British and Commonwealth belts to Michael Sprott
May - wins WBU heavyweight title after Ivory Coast's Augustin N'Gou retires
July - knocks out Mike Tyson
Williams' win has helped him shrug off his reputation as a boxer who choked on the big occasion.
"I just believe that what is going to be is going to be," he said.
"I'm relaxed - all you can do is go out there and do your best and that's my attitude now.
"I'm not going to worry about what might happen. I'm just going to go out there and do what I have to do.
"I don't think I've ever trained properly for a fight before this - because my training was so good this time, I felt so much more confident."
Williams' unexpected victory could propel him into the reckoning for a shot at one of the division's world titles, but the fighter was in no rush to make any decisions about his immediate future.
"I want a world title fight. Any of the champions would be good, but I've just got to sit back and see what's on offer."