In 2011, Haye lost his WBA title in a unification clash with Wladimir Klitschko.

And when asked about his reasons for making a comeback, Haye told Sky Sports News on Tuesday: “It is unfinished business.

“I always wanted to unify the titles and I got my opportunity against Wladimir Klitschko, and I don’t believe I fulfilled my potential that night. I believe I underperformed.”

Haye, formerly with Adam Booth, now has a new trainer in Shane McGuigan, the son of Barry McGuigan who also works with super-bantamweight world champion Carl Frampton.

And Haye added: “I have a new team, we are going to do things from scratch and I am going to go on and become heavyweight champion of the world.”

In 2013 Haye withdrew from proposed clashes against Manuel Charr and Tyson Fury due to injuries, with surgeons advising him following a shoulder operation on the latter occasion to seriously consider retiring.

Regarding his time away, Haye said on Tuesday: “Three-and-a-half years out of the ring is a long time and I have had injuries and operations.

“But I am fully fit now, feeling better than ever and looking forward to getting in amongst some of the big fights that are happening at the moment.

“When you have to put your arm in a cast and can’t move it for six months, you get really low and depressed – you can’t exercise, you put on unnecessary weight. It was probably one of the lowest times in my life. But I’ve come out of that now with a new lease of life.

“I had seen what Shane has done with Carl Frampton, and I always thought if I was able to get back into the ring, I’d like to work with Shane.

“We talked a long while ago and when I was physically ready to start punching again, I went down the gym and have not looked back – it has been one great session after another.

“A lot of people are worried about the three-and-a-half years off, but I believe that after that period, I am going to be a better force than I was when I was in my alleged heyday. I believe I am in my heyday now.”

Thirty-three-year-old De Mori, ranked in the WBA’s top 10, suffered the only defeat of his 33-bout career in 2004. He has won 30 times, including 26 knock-outs.

Haye has 26 victories (24 KOs) and two defeats on his record, the last loss being that in 2011 to Klitschko.

After claiming various world titles at cruiserweight, Haye stepped up to the heavyweight division and took the WBA crown in 2009 by beating Nikolai Valuev.

That belt was retained in subsequent fights against John Ruiz and Audley Harrison, but then lost to Klitschko, a clash after which Haye insisted his performance had been undermined by having broken his toe pre-fight.

A brief retirement followed, before an infamous brawl with Chisora prompted it coming to an end with a contest between the pair which saw Haye triumph in the fifth round at Upton Park.

In terms of potential future fights, Haye has mentioned the likes of Klitschko and Fury – who face each other on Saturday – as well as Anthony Joshua and his forthcoming opponent Dillian Whyte, and current WBC champion Deontay Wilder as names he has an eye on.

Meanwhile, he is backing WBA, WBO and IBF king Klitschko to defeat Fury at the weekend.

“For me, this is Tyson Fury’s first fight at genuine world-class level,” Haye said.

“I feel he will fall short – in fact, that he’ll fall pretty long to be honest.

“He is a big guy and in boxing anything can happen, but I would probably give him a one-in-20 shot.”