Joshua weighed in at his heaviest weights for the bouts against Klitschko and Takam, weighing in at 17st 12lbs and 18st 2lbs for those respective fights, but Hearn expects Joshua will be "leaner" and "lighter" for his match-up in Cardiff on March 31 against WBO world champion Parker.

"I can't see him coming in more than 17st 8lbs or 17st 9lbs, which would be half-a-stone lighter than the last fight. Maybe he will be even lighter," Hearn told Sky Sports.

"He feels amazing. I was on FaceTime with him and he got on the scales -- he was 17st 7lbs on Sunday night. He'd had a weekend of replenishing.

"From the day after his Takam fight, all he has been thinking about is how he can improve, get a bit leaner, improve the jab, improve the footwork. He is obsessed with improvement.

"I watched him spar 12 rounds last week. His footwork is so much better -- he is gliding on his feet, he has got faster hands. He is so meticulous in camp, like nothing I've ever seen.

"He is lighter and started camp earlier so they aren't having to exhaust him. He is working hard, but much smarter. So far, this is the best camp he's had. Coming in lighter, he feels great."

Hearn also provided an update on who Joshua's next opponent could be assuming Parker is defeated, with a fight in the U.S. against Jarrell Miller or a WBA mandatory, most likely against Alexander Povetkin, the most likely match-ups.

"Anything could happen," Hearn added. "Jarrell Miller could be beaten [by Johann Duhaupas], we might fight Deontay Wilder next, the WBA might call their mandatory. If we box in America and it's not Wilder, Miller will be the perfect guy.

"At some point the WBA will call a mandatory, I think this summer. I think we will have to fight Alexander Povetkin this year so it could be next."