A vintage Joe Calzaghe outpointed Mikkel Kessler and claimed the undisputed super middleweight crown at Cardiff's Millennium Stadium.
Calzaghe is now undefeated in 44 pro fights
Calzaghe, making the 21st defence of his WBO belt, started slowly and was hurt on a number of occasions by Denmark's WBA and WBC title-holder.
But the home favourite took control in the middle rounds and dug deep down the stretch to secure a unanimous decision.
Calzaghe, unbeaten in 44 fights, was watched by an estimated 50,000 fans.
The encounter is likely to be Calzaghe's final fling at 168lb and he could now fight American great Bernard Hopkins at light heavyweight in 2008.
The 35-year-old Welshman was forced to draw on every inch of his experience and skills to repel the Dane by scores of 117-111, 116-112 (twice) on the judges' cards.
"Calzaghe produced another top-class performance when he needed it most," said BBC Radio 5 Live boxing correspondent Mike Costello.
"He could have made it easier when he got in front by standing off his man, keeping everything at range and not giving Kessler any chance to connect.
"But he's not like that - the guts and the instinct, which have made him the champion that he is, drew him back into the danger areas time and time again."
There were a number of anxious moments for Calzaghe in round one as Kessler, who came into the fight with a 39-fight unbeaten record, landed with some crisp left hands.
Calzaghe looked to have scored a knockdown in round three but referee Mike Ortega ruled, correctly, that Kessler had slipped.
Calzaghe was stiffened by a huge right cross and a couple of booming right uppercuts in round four and it looked for a moment as if age might be catching up with him.
But the Newbridge southpaw rallied in the middle rounds, tightening up his defence and bouncing in and out of range to good effect.
He enjoyed a much better sixth and landed some good combinations at the beginning of the seventh before Kessler retaliated with a long over-the-top right and some hurtful shots in round eight.
Calzaghe, however, retained his composure and it was he who looked stronger in the final third of the fight.
He had Kessler back-pedalling with a flurry of punches in round nine and again in the 10th before landing with two sharp uppercuts in the 11th as Kessler began to fade.
And Calzaghe was at his best in the final round, landing with hooks off both hands and closing out the fight, despite one final effort from the Copenhagen native.
"I knew it was going to be one of the toughest fights of my life, Kessler is a fantastic fighter in his prime," said Calzaghe.
"It's not bad for a 35-year-old. I'm so proud of my efforts, the efforts of my Dad and [promoter] Frank Warren who put this together.
"It's so sweet, I was struggling at the end, I was a bit tired. But I felt I controlled the fight and was proud of my performance.
"I realised after a few rounds the jab was too fast for him. When I put my boxing together he couldn't get past the jab.
"There was a bit of ring rust but I won the fight. I think it was a good performance by myself, I felt pretty sharp but made a few mistakes.
"Ten years a champion, four major belts - what else is there to do? Dig all those guys up - Roy Jones, Bernard Hopkins, let's do it.
"I think I've shown them in the States what I'm all about. I'm looking at fighting for another 12 months and hopefully Hopkins will come out of hiding."
An emotional Warren said: "It's my best moment in sport. I'm so proud of him. He gave everything."