The Cambuslang fighter joined such greats as Jim Watt and Ken Buchanan with a unanimous points decision after 12 rounds in Glasgow.

After the fight a jubilant Harrison said: "I feel unbelievable - it's unbelievable to put on a good performance in front of 5,000 people.

"I'd like to thank my trainer, my dad and my manager."

Manager Frank Maloney added: "It was a great win. We've waited six long years and he's the champion of the world. He's now in the elite featherweight bracket."

Both fighters started cautiously, but the 27-year-old Scot had the better of the first round.

But Chacon had won the title by beating Hungary's Istvan Kovacs in Budapest - and it would take more than an intimidating atmosphere to unsettle him.

And he came back strongly to shade the second.

Harrison enjoyed his biggest round of the fight in the fourth, which started with a big right hand to the champion's chin.

Chacon, who has never been knocked out, was soon pinned against the ropes - and a fierce right saw him marked under his right eye.

The momentum remained with the home favourite in the fifth, and a crunching left seemed to rock Chacon.

The Argentine came back with some vicious punches and enjoyed the better of the seventh round.

McCullough target

But that was short-lived as Harrison had the champion in trouble twice in the eighth after a succession of crushing blows to the body and the head.

Both stood toe to toe in the tenth, but a fierce left to the chin from Harrison rattled the champ again.

Chacon, who bloodied Harrison's nose in the 11th, was on the floor in the 12th but was deemed to have slipped on grease.

Both fighters finished strongly. But it was Harrison who was hoisted aloft after a unanimous verdict, and he now seems set to defend his title against Wayne McCullough.