Williams made quite an impact both on and off the field during New Zealand’s triumphant victory over old foes Australia in the World Cup final on Saturday. Williams – who replaced Conrad Smith at half-time – made an immediate impact after coming on; making two offloads in his first two touches of the ball – sending Ma’a Nonu away for his beautiful 40-metre try with his second – as well as stripping Drew Mitchell of the ball with his third.

As Williams celebrated on the field after the whistle, a young jubilant fan – Charlie Lines – ran onto the Twickenham pitch and tried to join the All Blacks’ lap of honour. Lines was tackled by a security guard but was helped up by Williams, escorted back to his family in the crowd and then, to his amazement, was given Williams’ World Cup winners’ medal.

Williams said: “A young fella snuck onto the field somehow but when he was coming up to give me a hug, he got smoked by a security guard, full-on tackled him. He was only eight (in fact, Lines is 14) and the other fella was a big man so he was lucky he didn’t break his ribs or something.”

Ecstatic: Charlie Lines is jubilant as Sonny Bill Williams gives him his medal. Photo: Getty images

Fittingly, World Rugby gave Williams a new medal at the glamourous awards ceremony. Williams was given a rousing reception, and before he was invited onto the stage, the master of the ceremonies said: “World Rugby would like every winner to go home with a medal and they have found the final one.”

Williams thanked World Rugby for the “gift” of a new World Cup winner’s medal and tweeted a selfie of his gratitude.

When questioned about the impact he had made on the final outcome of Saturday’s match, Williams spoke warmly of Australia’s form during the World Cup and said triumphing with the New Zealand “brotherhood” gave him the greatest satisfaction.

He said: “I knew I’d been playing some really good footy at this tournament but I didn’t want to leave it there. I just wanted to go out there and make an impact. I knew I was going to get some time. I was just pleased that I didn’t drop the ball on the brothers, especially the ones that are leaving. It’s a pretty happy dressing room back there and importantly it’s a happy country back home – all our friends and family back home who supported us. And not just them, the public support has been immense. I’m just really happy to get that win in the end.”

Brothers in arms: Nehe Milner-Skudder, Ma’a Nonu and Sonny Bill Williams pose with the Webb Ellis Cup. Photo: Getty images

He added: “I think Australia have probably been the form team all tournament. We spoke about it during the week, that games aren’t won unless the forwards are going forward and they definitely made an impact. And that pass to Ma’a, I just closed my eyes and threw it… Na! He just did his magic and we were lucky enough to score there.

“Obviously I’ve got a couple of close friends who play for Australia, but there always has to be a winner and there always has to be a loser. It could easily have been us on the other side of the draw. You can’t say too much when you see them afterwards, but that’s the sport we play. We love it.

“Australia were quality and thank God we hung on. It was getting pretty tight there, but the boys dug deep and that’s where you learn, that our team is more than a team, it’s like a brotherhood. You bust your arse, you cover tackles, you just push that little bit extra because it’s the brotherhood and you’re doing it for each other. You’re just really, really happy.”

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Williams said the experience of the All Blacks side meant they were ready to face all the challenges the World Cup final threw at them and make sure their retiring stars finished their Test careers on a high note. “We probably didn’t say too much before the final, but we knew we had to step up and we knew we had to send the rest of the boys out as winners too.”

A wonderful moment, befitting of a great final contested by two titanic teams, in a fantastic World Cup.