James DeGale made history as the very first British-born fighter to follow an Olympic gold medal success with a world title after he claimed the vacant IBF super-middleweight belt with a unanimous decision victory over Andre Dirrell in Boston, Massachusetts.

The Londoner, who achieved public recognition at the Beijing Games in 2008 and boasted a record of 21 wins from 22 professional contests before tonight, started with real purpose, taking a notably chippy first round against his talkative opponent with enthusiasm before rocking Dirrell massively in the second.

Despite having blood oozing from a wound below his right eye, DeGale remained focused under considerable pressure and unleashed a devastating overhand left that stunned the American and sent him sprawling to the canvas for only the second time in his career.

With Dirrell in a daze, the confident 24-year-old sensed his opportunity to inflict further damage. He proceeded to go for the jugular once more and it paid dividends in the form of another impressive knockdown.

Referee Leo Gerstel then invoked a standing count, but Dirrell survived the remaining seconds before the precious bell and made it back to his corner for a period of crucial recovery.

DeGale landed another sizeable left in the closing stages of the third, but 'The Matrix', who lost his only previous title fight against Carl Froch back in 2009, showed admirable resilience to recover well in rounds four and five and began to dictate the tempo while remaining mindful to keep a safe distance to avoid getting tagged with anymore huge shots.

A further close round followed in the sixth with both men landing punches in a furious late exchange and at this point the feeling appeared to be that DeGale was failing to capitalise on his early momentum by not continuing to seize the initiative against an evenly-matched opponent who was evidently capable of reducing the deficit.

Dirrell has remarkably quick hands and he let fly with two separate flurries that peppered DeGale in a blur of attacking aggression that had been notably absent in the initial stages. Most of the shots failed to find their intended target, but there was no doubt that the Michigan native was back in the contest now.

The eighth looked to belong to Dirrell again as he worked his own left hand to good effect. DeGale appeared to be struggling somewhat with the pace of the contest, meanwhile, and was reluctant to throw anything in response. The two fighters clashed as the bell sounded for the end of the ninth round as the war of words and theatrical goading continued.

With the bout balanced on a knife edge, it seemed that whoever could muster the superior effort over the final two rounds would likely have the edge on the scorecards and it was DeGale who just about did enough with a strong and busy finish in the 12th that was at odds with his efforts in the middle half of the evening.

The judges returned scores of 114-112, 117-109 and 114-112 and DeGale could hardly contain his delight after having his hand raised before issuing a confident challenge to any future opponent in the division.

"I'm speechless," he said after being handed the title that previously belonged to Froch.

"My whole career, all I've been building up to is winning a world title. And I've finally done it. It's an unbelievable feeling. I'm world champ. I'm world champ. I made history. First [British] Olympic gold medalist to be a world champion.

"See when I was coming in and out, throwing punches over the top? I'm back now, i'm injury-free. I will take on any super middleweight in the world. I'm hard to beat when I'm at my best. I'm telling you, I'm hard to beat."