He promised it would be easy, and predicted the end would come within two rounds. Prophetic and powerful, David Haye was right on both counts, as last night he bludgeoned domestic rival Enzo Maccarinelli to defeat inside six minutes at London's O2 Arena. In doing so, he unified the cruiserweight division by adding the Welshman's WBO world cruiserweight belt to his own collection of WBC and WBA world titles.

Promoter Frank Warren labelled the battle of the 27-year-old British cruiserweights as the country's biggest ring collision for fifteen years, and, motivated by hype and the promise of a classic, 18,000 fans crammed into the north Greenwich venue in the early hours of Sunday morning. And with the first bell scheduled to toll at around 2am, the anticipation reached unbearable levels as the two fighters made their way to the ring.

Many years in the making, this was the moment they had been waiting for. Haye, the showman, the capital's playboy, against Maccarinelli, the humble, softly-spoken man from the valleys. They only thing they shared in common was a propensity to win cruiserweight bouts via knockout.

Given this knack of conjuring knockouts – typically quick ones – most in the arena expected an abrupt finish to the unification match. The consensus opinion was that Maccarinelli had as much of knocking Haye out as Haye had of knocking Maccarinelli out. Whoever lands first, they said, over and over, like confused cult leaders. In the opinion of many, there could be no possible way either Haye or Maccarinelli stood up to any sustained punishment. The finish, they said, had to be quick and devastating.

Yet these assumptions seemed ill-founded during the first three rounds of the fight. Both men landed early left-hooks, but neither were anything like definitive blows. Maccarinelli's caught Haye off balance and forced a momentary stumble, while Haye's retort, thrown later in the round, smacked his foe in the face, but failed to so much as budge him. And so, two flashpoints aside, the opening round was marked up as part of the feeling-out process and, in the eyes of harsher critics, something of a bore.

The fight lived up to expectations in the second round, however, when Haye suffered a minor slice above his eye, realised blood had been spilled, and then set about ending matters as swiftly as possible. Maccarinelli, taken by surprise, was caught in the crossfire, and despite his best intentions to stay away and take Haye into the second half of the fight, there was no escaping the lightning fast right hands that were launched his way. Time and time again Haye measured his counterpunches to perfection and cleverly walked Maccarinelli on to them.

After eating two flush right hands in the centre of the ring, the Welshman decided to move. But this only opened more space in which Haye could pounce. So that is exactly what he did, firing further rights, one of which caught Enzo on the jaw and sent him spinning towards the canvas. Follow-up blows from Haye applied the exclamation mark. Maccarinelli was down and in grave danger.

Referee John Keane followed the floored fighter's unsteady totter around the ring, a look of indecision etched upon his face. He could see what we could all see. Maccarinelli's legs had betrayed him and, though his heart remained willing, his body and mind had just about given up. Mercifully, Keane sensed this and signalled an end to both the Swansea man's night and reign as WBO world cruiserweight champion.

As a slight stream of blood crept down the side of his face, Haye raised both fists towards the sky and prepared his waist for the arrival of an additional world title. Unified and undisputed, he was also, evidently, a fighting fortune teller.