The world will be a better place "if we can all try and be a better friend from time to time".

It is what has driven him to raise more than £7m for charity in the last three years.

Aged 14, Sinfield met a 12-year-old Rob Burrow at rugby league side Leeds Rhinos. Twenty-eight years later, they are still firm friends after a glittering career in which Sinfield became the Rhinos' most successful captain, winning seven Super League titles.

In 2019, Burrow, who is now 40, was diagnosed with Motor Neurone Disease. Sinfield sprung into action.

First, in 2020, he ran seven marathons in seven days - seven being Burrow's shirt number.

Then in 2021, he set out to run 101 miles from Leicester - where he was coaching - to Leeds and ended up running 104 miles after getting lost twice.

Finally in 2022, Sinfield ran 40 miles a day for a week, ending the challenge at half-time in the men's Rugby League World Cup final.

"I do it because that's what mates do," he said of his challenges.

Speaking on BBC Two documentary Kevin Sinfield: Going the Extra Mile, he added: "It shows you that with a will and a fight, you can get a lot of things done."

France to test Sinfield defence

It is evident from his successful stint as Leicester Tigers defence coach, during which he helped them win the Premiership, that Sinfield brings the same commitment to his work.

England will need every bit of it as they look to rebuild six months out from the World Cup after a disappointing end to Eddie Jones' tenure as head coach.

When Sinfield asks for more from his players in training, there can be no questions. He has put himself through far worse.

With Grand Slam-chasing Ireland to come in the final round, France's talented backline are likely to present the toughest test of Sinfield's maiden Six Nations so far at Twickenham on Saturday.

The ducking and weaving of scrum-half Antoine Dupont, the nifty tricks of Romain Ntamack and the pace of newcomer Ethan Dumortier on the wing will all combine to try and find a way through.

On top of that, Sinfield's coaching skills will be held up against the shining example of defence guru Shaun Edwards' influence on France.

Sinfield describes Edwards - winner of three Grand Slams coaching Wales and one with France - as "a legend" and his coaching achievements as "incredible", telling BBC Sport: "The way the French play, the flair and physicality, the power, the pace. They are an outstanding team. It will give us an indication of where we're at."

Sinfield only joined England in December and, after such a short time together, their defensive efforts got off to a shaky start against Scotland in February.

A nerve-settling victory against Italy followed, before another win in Cardiff in England's last fixture on 25 February.

England have conceded seven tries so far this Six Nations - with only Ireland conceding less on four - and have conceded the least penalties of any side with 23.

But they have missed more tackles than any other team, with 84. Conversely, France have missed 61 and Sinfield's message to players was simple after defeat by Scotland: "You can't miss tackles, guys."

'Mutual respect' with Edwards

Sinfield is over a month into the tournament now and the former Great Britain and England rugby league player's impact will reveal itself further.

League coaches have proven to be popular in union, with Edwards the standout example. Ireland head coach Andy Farrell has also made a great success of the switch and Wales' defence coach Mike Forshaw came from the other code too.

Speaking on the Rugby Union Daily podcast, Edwards explained: "It's just the emphasis on defence [in rugby league].

"We've always been brought up that you have to practise defence in 25-30% of your training sessions.

"In rugby league you don't have to win the ball. You don't have to spend any time on your set-piece. In union you have to spend a lot of time [on set-piece]."

Sinfield only made the move from league coaching to union in 2021 and when he did, he got in touch with Edwards, of whose playing and coaching he says he is "a huge fan".

"We had three or four conversations over Skype sharing information," Edwards said.

"He helped me a bit. I was explaining to him about rugby union: it's always a contest for the ball, you can lose the ball at any time.

"There's definitely a mutual respect between us."

Another big challenge to come?

Given what he has put himself through to support those suffering with motor neurone disease, no doubt the England players hold Sinfield in high esteem. Fans will hope this translates into a well-drilled defence to match France's on Saturday.

Of his off-field exploits, and the three great challenges he has taken on so far, Sinfield says: "Most great books and films are a trilogy. There's a World Cup at the end of the year and my focus needs to be on that and the team.

"For me to be a good coach and get the best out of myself, I need to be able to run. There is a caveat in all this, which probably relates to the Rocky films.

"Rocky isn't a trilogy, but I would say that Rocky IV is probably my favourite. We'll see."