The prop, who appeared in all three Test matches on the 2017 British & Irish Lions Tour to New Zealand, spent ten years with Battersea and still goes back to the club whenever he can.
In 2020, he is one of the world’s elite front-rowers but when he toured with the Lions three years ago, Sinckler hadn’t made a single start for England – although his impact off the bench for Eddie Jones’ men had already been colossal.
His Lions call-up was celebrated by the Ironsides, where he had once cut his teeth as a bulldozing centre – scoring tries for fun in Earlsfield, just down the road from Twickenham, the home of English rugby.
Sinckler’s path into the sport is well known, and Marcus Bailey – who progressed to play senior rugby for the Ironsides – was alongside him at the beginning, witnessing a future Lion grow each week.
“I have known Kyle since I was seven and a lot has been written about the fact that he was quite a big chap when he was younger, and he was a bit too physical playing football,” said Bailey, speaking ahead of the 2017 Tour.
“Me and mum suggested he come down to play rugby and he took to it like a duck to water. I played alongside him for ten years and saw him develop into the player he has become.
“When we were in age-group rugby he was an inside centre, which is quite funny because he was the same size as he is now!
“He was so much bigger than anyone else and he was just this massive pacy inside centre, and now he is obviously a tighthead prop and it is great to see.
“Our gameplan was get the ball to him and he would score. Because he was so quick for a big lad and twice the size of everyone else.
“We just shipped it out to him, he would run a tight line and he would knock a couple of lads down. It was like a battlefield when he ran through.”
Sinckler still retains a deep affection for the club, and Bailey admits they celebrated as much as he did when he was called up for the 2017 Lions Tour.
And Bailey says that even growing up, the prop was destined for big things in rugby.
“He used to say ‘I just like running into people’ when you asked him why he was so good, but he always had that drive to succeed,” he added.
“That comes from his mum, his home and the club. I was so happy for him [when he got called up for the Lions]. Everyone at the club was so happy – we put a big banner up and it was a real local success.”
From @IronsidesRugMin to @lionsofficial… today, we are proud. Well done @KyleSinckler 👏🏼🦁#onceanIronalwaysanIron #fearnaught #oneclub https://t.co/hOUOo871n4
— Ironsides Rugby Snr (@IronsidesRugSnr) April 19, 2017
Sinckler’s success has inspired a new generation at Battersea, a club which puts a strong emphasis on youth development.
For a club tucked away in a busy part of south-west London, where there is plenty of local competition, they have done incredibly to attract over 1,000 young players aged between six and 18.
It is now one of the largest junior clubs in the country, a far cry from where the junior section started 25 years ago when three original founding members started coaching just 20 players.
“Our location is really good,” said Bailey. “Everyone has their own lives in south-west London. They are all in their own mind and are going about their own business.
“But at the club we all know each other. It is a place where people come together. That is a testament to the club.
“In the 2014-15 season we got to a final of National Junior Vase at Twickenham where we ended up beating Northallerton 23-7.
“We took 3,000 people from the club and then with all of their families and friends, you can imagine how great the atmosphere was.
“It brought a lot of the club together and was the first step in getting more of youngsters involved. Now that’s our big focus.”
Playing for @Harlequins, @EnglandRugby and @lionsofficial but @KyleSinckler‘s biggest accolade is this one 👇🏻👇🏻👇🏻
2,3 #rugby #oneclub https://t.co/UtgOG6lAtD— Ironsides Rugby Snr (@IronsidesRugSnr) May 22, 2017
Sinckler may be the standard-bearer and the club’s poster boy for success but, with a wave of talent breaking through, he may not be alone for long.