The Welshman hammered Mario Veit to the canvas in the opening minute with a crushing left hook and followed up to send the German crashing down for the second time.

Veit, like Calzaghe entered the bout with an unbeaten record from his 30 fights, struggled to his feet and under a barrage of further punches referee Mark Nelson called the contest off.

Calzaghe had started a heavy favourite against Veit, who had compiled his record out of the world class which Calzaghe has inhabited since wresting the title from Chris Eubank in 1997.

Few could have predicted the sensational nature of his win which, following so soon after the demise of both Lennox Lewis and Naseem Hamed, has now established him as the leading British boxer of the moment.

Calzaghe's promoter Frank Warren had called on his man to make the most of his big chance and had promised him a long-awaited debut in America this summer if he disposed of the former chef from Cottbus.

Veit had looked nervous as he waited for the champion to enter the ring and refused to lock eyes during the pre-fight ritual.

His plans to box neatly behind a flicking jab were exposed as Calzaghe charged across the ring to meet him on the sound of the opening bell.

Joy for Pryce

Calzaghe's stablemate Bradley Pryce had earlier been a shade fortunate to retain his unbeaten record with a hard-fought points win over Londoner Jason Hall.

Pryce, who picked up the lightly regarded WBO intercontinental lightweight title for his troubles, won a unanimous verdict 116-113, 115-113, 114-113.

Calzaghe, whose career has been held back by hand injuries, could not hide his delight over his victory.

"I've been frustrated for the last three years. Although I've said to the public that I'm the best fighter in Britain, Lennox and Naz have taken all the plaudits," he said.

"But they got beat and so obviously it all rested on my shoulders tonight.

Trip across the Atlantic?

"There was a lot of pressure on me.I was fighting in front of a great home crowd. Basically, I could not let anyone down tonight and it's for the fans that I've knocked him (Veit) out in the first round.

"I felt so strong, so powerful, I made the weight comfortably.

Calzaghe admitted he had been inspired by the emotional backing he received from Welsh fans in the Cardiff International Arena.

"Basically they're the best fans in the world," he added.

"They deserve to have a world champion. I love fighting in Wales, I love fighting in Cardiff. They really spurred me on."

Promoter Frank Warren confirmed that Calzaghe should now fight in America and refused to give up on the possibility of securing a fight with American light-heavyweight Roy Jones.