The 31-year-old Ospreys player saw off competition from Wales captain Ryan Jones, New Zealand fly-half Dan Carter, Scotland captain Mike Blair and Italy skipper Sergio Parisse to land the award at a gala dinner in London.

Williams scored six tries in the 2008 RBS 6 Nations and was named player of the tournament as Wales won the Grand Slam.

He broke Gareth Thomas’ try-scoring record in the title-clinching victory over France and has scored 43 tries in 60 Tests for his country - 14 of them in his last 13 Tests - after making his debut against Italy in 2000.

Swansea-born Williams has also represented the British & Irish Lions, winning caps against Argentina and New Zealand three years ago.

Williams could not contain his pride at having scooped the award and said: “It’s quite mad to be honest.

"It's been a hell of a year and this has just capped it off really. It's the biggest honour you can get as an individual in rugby and it's totally overwhelming."

He added: “Just being nominated was humbling. And to receive the award from Bryan Habana, who is one of the best - if not the best - winger in the world means so much to me.”

“I was more nervous up there (on stage) than I was facing the haka yesterday!”

Williams’ award was the only one not to go to New Zealand, with the All Blacks taking IRB Team of the Year and Graham Henry named IRB Coach of the Year.

"It's been very satisfying," said former Wales coach Henry.

"There have been 15 or so players who left us after the Rugby World Cup to play in this part of the world so it's great to have a team that's relatively young and inexperienced come through and do the business."