Sonny Bill Williams says winning the New Zealand heavyweight boxing title eclipsed anything he achieved during a stellar cross-code rugby career.

He retired in March and has since returned to boxing to add to the seven fights he won between 2009-2015.

"It was awesome," he told BBC Radio 5 Live's Adrian Chiles.

"Winning the New Zealand heavyweight title belt was amazing. I didn't grow up boxing. It was so unfamiliar for me."

Williams turned to boxing when he was left in debt after buying out his Canterbury Bulldogs contract, the league side he left in 2008, before moving to French union club Toulon.

"It started off through necessity because I had to pay bills but it lit a fire inside me that I could never put out and it accumulated in me thinking I would try and win that belt. I did it and it was awesome," he added.

"It would be a dream come true to fight against that type of calibre of fighter [Tyson Fury]. I am an avid boxing fan. I watch their training and see what they do and love boxing."

Williams switched between league and union during his 17-year career, winning NRL titles with the Bulldogs and Sydney Roosters and the 2012 Super Rugby title with the Chiefs.

Aside from his World Cup victories with the All Blacks, he was also involved in the side that drew the 2017 series against the touring British and Irish Lions. He played his last game of rugby league with the Roosters in the semi-final loss to the Canberra Raiders in the 2020 NRL play-offs.

He was contracted to play in the 2021 season with Toronto Wolfpack, but the deal fell through after the Canadian team was denied readmission to the largely England-based Super League.

Williams improved his boxing record to eight straight victories in June when he beat Waikato Falefehi via unanimous decision, though his first fight in more than six years saw him suffer a second-round knockdown.