It is prayer time in the Williams household and Sonny Bill is leading the sunset Maghrib ritual with his brother, Jonny, and cousin, Eka, in the corner of the living room.

‘Sorry, bro, it will only take a few minutes,’ says the converted Muslim, who has just dished up a generous serving of chicken fajitas at his Auckland home.

His wife, Alana, is playing with their 18-month-old daughter, Imaan, in the house where the walls are strikingly bare of photographs and sporting memorabilia.

Sonny Bill Williams takes on the Australia defence during New Zealand's World Cup semi-final win in October

‘You can’t have eyes on the wall or the angels won’t come in,’ says Williams. ‘That’s what we believe. I don’t need a pool room with medals and everything hanging up.’

Sipping camomile tea with honey, Williams is embracing Friday family time. Weekends used to revolve around VIP guest-lists at nightclubs but here rugby league provides the television entertainment.

‘I grew up in a commissioned house in the next suburb over, Mount Abbot,’ says the All Blacks double World Cup winner. ‘It was a two-bedroom house with me, my brother and my two sisters. Mum and dad slept in the lounge and we didn’t have wallpaper. All my family lived close by and Eka was our scary older cousin that looked after us. He’s been in and out of jail a lot.’

Working as a labourer and a stock-taker during his teenage years, Williams’s motivation was to buy his mother a house after seeing her ‘struggles’.

His playing career took off in Australian rugby league with the Bulldogs, before taking up union and representing the All Blacks, with the unpredictable journey now reaching the Rio Olympics with New Zealand Sevens.

Williams runs clear from would-be Leeds tacklers playing rugby league for the Canterbury Bulldogs in 2005

‘It’s been a long while but, thank God, now I’ve been able to get my mum a house,’ says Williams. ‘My manager in my early 20s put me into a bad investment and I was in debt. People thought I was living the dream in Toulon but I had to pay NZ$750,000 (£400,000) to get out of my contract.

‘Never in my wildest dreams would that young fella that went to Australia be here right now. It’s such a blessing to be with my wife and children. I used to be a bit of a scallywag. I did a lot of bad things and went off course but Allah was with me.’

Williams has gone from ratbag to role model.

His global popularity peaked when he gave away his winner’s medal to a young, star-struck pitch invader at Twickenham last year. That generosity shines through when, after providing dinner, he insists on a 50-minute round trip to drop me back at my hotel.

‘My wife has already said that if, God willing, I make it to the Olympics and win a medal, then it’s going straight on my daughter — I can’t give it away!’ he says. ‘The sevens has rejuvenated me. My sister’s in the New Zealand Sevens squad, too, so it’s massive for our family.’

Williams gives his medal to a young All Blacks fan after his second World Cup win at Twickenham last year

The New Zealander side-steps a defender during his spell with French giants Toulon back in May 2010

As the only Muslim in the squad, both in Sevens and XVs, Williams has to find a way to fit the Islamic prayer-and-diet lifestyle around the intensive schedule. ‘When I’m most happy is when I’m doing my prayers,’ he says. ‘When you travel you can compensate by joining the two afternoon prayers and the two evening prayers together, which is pretty sweet.

‘How can you not spare 25 minutes of your day to give thanks? I look at where I came from and feel blessed.

‘The chefs provide halal food. I get kind of embarrassed when they make a big deal out of it. I just want to fit in and be one of the boys, but at the same time faith is where everything comes from. If there’s no halal meat, I can eat seafood. If there’s no seafood, I’ll just have a shake or something. There are people worse off than I am.’

Take the Syrian refugees, for example, who Williams visited in Lebanon last year as a guest of UNICEF. Following the trip, the 30-year-old faced criticism from the charity when he shared graphic images of dead children with more than half-a-million followers on Twitter. He has defended his action, claiming more sports- people should use their profile to raise awareness of injustice.

‘The world’s wealth is controlled by one per cent of the population, something disgusting like that,’ he says. ‘When it comes to politics, I don’t understand Labour and Liberal and this crap. I can just see that something’s wrong when people can’t feed themselves and kids are playing in sewage.

Williams - here facing England in November 2014 - will return to the 15-man game after the Rio Olympics

‘It’s easy for me to say sitting here living the good life but why aren’t people seeing what’s going on in the real world? It’ll take, say, a billion dollars to provide basic needs across the world for refugees. How many billion dollars are there in the world? Why can’t people just own 100 million dollars and spread the rest. That’s enough, isn’t it?’

Williams pauses, chuckles and pushes out his heavily tattooed elbows: ‘Am I getting a bit off course, bro?’

Body art is considered sacrilegious under Islam and Williams will not be inking the Olympics rings, but is equally apprehensive about laser removal surgery.

‘No more tattoos for me, man. I’ve been getting lectures! I’ve got too many. That’s my bad boy days. I still feel like the same person but converting has given me contentment and happiness that I don’t know how to explain.

‘I used to be a stress head, annoyed if I dropped a ball in training. I grew up as a Christian. Islam is a way of life. Before, if I went out drinking or partying, I would be searching for something the next day with a hangover, getting eaten up inside.’

In pursuit of his Olympic dream, Williams will follow in the footsteps of his idol, Muhammad Ali, who also tiptoed along the border of controversy during his career.

Williams, too, enjoys setting foot in the ring and is undefeated in seven heavyweight fights, saying the transition to boxing was a tough challenge.

Williams fends off a jab from South African boxer Francois Botha in February 2013

‘It’s different to throwing a punch in a fight at school, the angles and that stuff,’ he says. ‘You’re thinking, “This is scary”, and it takes you to places you never thought you could go when someone’s trying to knock your head off.

‘Muhammad Ali and Malcolm X are two of the men that shaped my life. Muhammad Ali more so, not just because he’s a boxer, but because he converted to Islam and stood up for what he believes in.’

Williams is hoping to return to the XVs arena after the Olympics and has one eye on next year’s British and Irish Lions series — just one small box on his ‘to do’ list. He said: ‘I would love to be part of a successful Lions campaign and the big one would be making it to three World Cups.