Joe Calzaghe secured one of the most significant victories of his 15-year professional boxing career this morning when he outpointed the American veteran, Bernard Hopkins, by split decision at the Thomas and Mack Centre. His 45th straight win cemented his place in the pantheon of great British boxers and set up a possible career finale against Roy Jones Jr, perhaps the finest boxer of his generation albeit another veteran now well in decline.

The best days of the 43-year-old Hopkins are behind him now, too, but he retained enough of the old craftiness and clinical technique to floor Calzaghe in the first round and ask serious questions of the 36-year-old from Newbridge in Wales. While Calzaghe did not perform at his best – a fact which Hopkins’ ability to spoil and tie him up in close had much to do with – he demonstrated diamond-hard nerve to survive the crisis of the opening round and resurrect his hopes in the subsequent rounds in this desert town.

“My first trip to Las Vegas - my first fight in America – started like a nightmare,” said Calzaghe, who won The Ring light heavyweight title to go with the world super middleweight title which, in various forms, he has held for almost 11 years. “Hopkins was dirty, he tried to feign injury [when he gained a five-minute respite in the 10th round by claiming, dubiously, that Calzaghe had punched him low] and he cheated by holding and trying to spoil the fight almost the whole way through. I showed heart by getting up from that right hand in the first round and for coming through on the winning side over the rest of the fight.”

The right with which Hopkins decked the Welshman, short and straight down the pipe, was an ominous sign that he and his camp, led by trainer Freddie Roach, had done their homework and had figured out a way to beat Calzaghe. He managed to rise to his feet without his legs betraying him further but he was clearly shaken. That his confidence was not altogether eroded is testament to the character of this unique fighter from the Welsh valleys. Hopkins continued to boss the next couple of rounds by utilizing his jab, maintaining a tight guard and by tying up Calzaghe at every opportunity. He also demonstrated that his right hand remains a potent and accurate weapon and Calzaghe’s resurgence only happened when he found a way to avoid the most dangerous punch in Hopkins’ arsenal by dipping forward at the waist and allowing it to slip over his shoulders.

He was not successful all of the time, however, which made it an arduous assignment for the unbeaten Briton. Calzaghe won his first round in the fourth when he raised the pace and began to time Hopkins’ punches better. He made him miss and countered him effectively with his left hand. On several occasions he evaded Hopkins’ right hand and landed with his own left and at the end of the round he raised his right fist to the crowd, convinced that the tide had turned.

But the wily American veteran continued to make it difficult for Calzaghe, who managed to put his frustration to one side as he made the necessary technical adjustments. He landed a solid left cross in the opening minute of the sixth round and, significantly, he was avoiding now the hard and accurate shots with which Hopkins had been having success early on. Hopkins has built his career on working out other fighters and exploiting their weaknesses but Calzaghe’s cleverness and calmness under pressure was the key to his redemption in a bout which featured many ugly exchanges as the noble art took a back seat. Still, the official punch stats – for what they are worth – showed that Calzaghe landed over 100 more punches than Hopkins, at least confirming that he made a stirring rally over the middle rounds into the second half of the bout.

Another left cross by Calzaghe in the eighth round emphasised that he had found a way to penetrate Hopkins’ defences while not having to pay such a high a price. He landed several more and Hopkins began to lose the cool efficiency that had characterised his early work. When Calzaghe landed a low left hand in the 10th it gave Hopkins an excuse to buy time and he was allowed to rest for five minutes before referee Joe Cortez waved the two men back into action. Calzaghe’s momentum could not be stopped and he continued to press forward over the final two rounds to cement his victory.

“I knew that the fight wouldn’t be pretty but I won it and this is icing on the cake for my career,” Calzaghe said. “Winning a second world title is beautiful and we’ll see now where I go from here.”

Roy Jones, the former world middleweight champion, who won titles at light heavy and heavyweight, was seated at ringside, commentating for BBC Wales and the financial incentive to put this fight together will be huge.

“I’ve always been a Roy Jones fan and maybe we can do that fight,” Calzaghe added. “First I’m going to the Caribbean to have a holiday with my girlfriend [Jo-Emma] and then I’ll make plans.”

For Hopkins, the fifth defeat of his Hall of Fame career may turn out to be his swansong. “I don’t think that I lost the fight – look at me, I don’t have a mark,” he said. “I turned pro 20 years ago and to be able to leave like this tonight, with all of my faculties, is a blessing.”

Hopkins may retire with his reputation intact as one of the finest fighters of his era. Having made 21 successful defences of the world super middleweight title, Calzaghe’s capture of the light heavyweight title has cemented his reputation as one of the greatest British boxers in history.

Audley Harrison, the gold medallist at super heavyweight in the 2000 Olympic Games, stopped his American opponent, Jason Barnett, in the fifth round on the undercard. The 36-year-old Londoner was engaging in his first bout since suffering a third round knockout defeat against Reading’s Michael Sprott in February 2007 and 33-year-old Floridian Barnett was a compliant victim.

Harrison maintained his distance behind a right jab which ought to have been more assertive and his reluctance to throw his left hand extended the fight further than it should have gone. At the beginning of the fifth round Barnett, who had lost six of his 16 bouts, caught Harrison with a grazing right hand to the chin which caused the Londoner some alarm. But he responded quickly enough with a right hook to the body, despatching Barnett on the canvas. Referee Russell Mora waved it over at the 1:48 mark, despite Barnett rising at the count of nine.

“I felt a little rusty because it’s been 14 months since I’ve been in the ring but I was happy with my jab tonight. I got it working good,” said Harrison. “When my corner told me to start going downstairs that’s when I broke him down.”

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