Haye described the victory over Maccarinelli as "the final piece" in his cruiserweight jigsaw.
Once he had unified the Cruiserweight Division, Haye once again moved up to the Heavyweight division, defeating Monte Barrett at The O2 Arena in London on November 15th 2008, winning via TKO in the fifth round.
WBA Heavyweight Champion
Haye then confirmed that he would challenge the WBA champion Nikolai Valuev (50-1, 34 KOs) on November 7th 2009 on foreign soil at the Nuremberg Arena, Germany. Haye's former trainer Adam Booth claimed it was a fight that Valuev wanted; it was billed as David and Goliath. Haye weighed in at 217 pounds, almost 100 pounds less than his opponent.
Haye beat Valuev in a display of accuracy and efficiency, countering Valuev's misses, jabbing and circling his much larger opponent, he also came close to knocking out Valuev in the final round with a hard left hand, which made Valuev stumble, going on to win by a majority decision with scores of 114–114, 116–112, and 116–112.
Haye is the first and currently only boxer in the history of the sport to be seven stone or more lighter than an opponent in a World title fight and still come out victorious.
On April 3rd 2010 Haye defeated John Ruiz in his first WBA title defence at the Manchester Arena by TKO in the ninth round after knocking him down no less than four times during the fight.
This was only the second time in his career Ruiz had ever been stopped, After the fight, Haye immediately called on both Klitschko brothers.
On November 13th 2010, Haye defeated Harrison with one minute, seven seconds remaining of the third round by TKO. In the early stages Harrison staggered to his feet after being knocked down, only for Haye to immediately pounce right back on him, hitting him with another flurry of punches. The referee intervened and ended the bout.
Haye's plans to unify the heavyweight division developed as it was announced that Haye and Wladimir Klitschko had agreed to meet at the Imtech Arena in Hamburg on July 2nd 2011.
Wladimir Klitschko v David Haye was a heavyweight unification fight for the WBA, IBF, WBO and The Ring heavyweight titles, the fight taking place at the Imtech Arena, Hamburg, Germany on July 2nd 2011.
The fight united the Nation and reached a global television audience of 500 million viewers in 150 countries.
Unfortunately, it was not Haye’s night and Klitschko defeated him by a unanimous decision to become the unified WBA (Super), IBF, WBO, and The Ring heavyweight champion.
In a move to finally settle notable bad blood between Haye and fellow Heavyweight Derek Chisora, Haye and his promotion team announced that he would fight Chisora at Boleyn Ground, Upton Park, London on July 14th 2012.
Haye won the fight with a fifth round stoppage in front of over 40,000 spectators. Knocked to the floor in the fifth round, receiving a count of eight, Chisora recovered only to be floored again in the same round. Referee Luis Pabon decided Chisora was unable to continue signalling the end of the contest.