"I have been privileged and blessed to have been given so many opportunities in New Zealand rugby, starting with Canterbury back in 2010, as well as the Crusaders and Chiefs, Counties Manukau and, of course, the Blues and All Blacks. I'd like to thank all those fans in New Zealand and around the world who have supported me," Williams said.
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And in a video, he told Toronto fans he was looking forward to his move. "I'm not coming over for a holiday, though my son might be..." said Williams, cradling his boy.
"I've also appreciated the support of many people at NZR, particularly the Chairman Brent Impey and Head of Professional Rugby Chris Lendrum. Brent is a thoughtful person who I've enjoyed talking to about issues affecting our game, while Chris has been awesome to deal with over the years, has always been fair with me, and I've always been grateful for his support.
"I'd also like to thank everyone involved in the All Blacks family. I never dreamed that I'd play in the black jersey for ten years playing alongside some of the legends of the game, and I'm grateful for the support of so many people in helping me grow as a footy player over that time.
"Finally, to the players I've been privileged enough to play with. I've enjoyed every moment being with the brothers and that will be the biggest thing I will miss: the camaraderie and fun with my fellow players and being privileged to suit up with them and go out and do what we love. It's been a pleasure.
"Alhamdulillah, I have been blessed."
The Toronto team is on the lookout for big-name signings following their promotion from the second-tier Championship and were keen on signing the All Blacks star.
The record deal will see Williams earn around four times the wages paid to NRL superstar Daly Cherry-Evans ($10 million over eight seasons) and AFL superstar Lance Franklin ($10 million over nine seasons).
Williams won the Rugby World Cup with New Zealand in 2011 and 2015 and last played professional rugby league with the Roosters in 2014.
Other rugby league and union teams were rumoured to be in the hunt for Williams' signature after his contract with New Zealand Rugby ended following the All Blacks' win over Wales.
Toronto had a competitive advantage over interested rivals of being able to sign Williams as a Super League marquee player where just $300,000 of his salary will be included in the team's salary cap.
McDermott said recently his team wanted to bring in a David Beckham-type player to do for the Wolfpack what the former Manchester United favourite did for LA Galaxy — and that Williams fits the bill.
The Wolfpack, a Canadian franchise, is funded by Australian mining billionaire David Argyle and will make its debut in the Super League next year after winning promotion by beating Featherstone Rovers.