Wladimir Klitschko has warned Anthony Joshua he will be facing his Everest when they fight at Wembley Stadium on April 29.
The 41-year-old is bidding to win Joshua's IBF heavyweight title and the WBA belt last held by Tyson Fury in front of what is expected to be a post-war record crowd of 90,000 for a boxing event in the United Kingdom.
He represents the biggest challenge of the 27-year-old Joshua's career, in which he has so far fought only 18 times and barely at world level.
In contrast Klitschko's only defeat in 11 years came against Joshua's compatriot Fury, a vastly different fighter. After the Ukrainian dismissed suggestions he is in decline, he compared his exceptional longevity with the world's highest peak, and the scale of the task Joshua has to overcome.
"Please excuse me and this may sound arrogant, but for example, a parallel: Mount Everest, the highest mountain in the world," Klitschko said.
"It's there. It's been there for a long time and will be there for a long time. You can climb it during a certain period of time: during two weeks in April I believe.
"You can get to the top and say 'I conquered Everest'. Then you've got to run down because it's going to take you down if you miss the time.
"After you're down, a lot of people died there. Some made it, not many, but some made it back. But Mount Everest is still there. Is Mount Everest defeated? It's still there and it's going to take another life this April.
"It's just the track of history. It was 27 years ago when I started (fighting as a professional) and I am still here. I have guys who have conquered me in certain periods of time out of the 68 fights.
"Four of them have made it out of a 21-year professional career. The rest didn't. Most didn't and the most amazing thing is I'm still here: they're not."
Klitschko also revealed the time he realised Joshua was no ordinary fighter.
In 2014 Joshua visited his training camp to help Klitschko prepare for his defeat of Kubrat Pulev, and the then-champion noticed the extent to which the young fighter tried to learn.
"He impressed me with his attitude," he said. "He was very raw. I have to say the truth, but he was the Olympic champion, he carried himself well.
"He was in the background and learning. Sometimes you need to be quiet and just watch. He was observing everything.
"It is unusual. I had Olympic champions in my camp and former world champions. The attitude is totally different. I liked AJ's attitude. He was not trying to impress anybody.
"He backed off, he was sitting on the side, not talking too much. He was watching, learning, asking questions. He was very polite. He was different than others at this stage of experience and achievements in sport."