The prop, who is set to Tour with The British & Irish Lions for the first time this summer, spent ten years with Battersea and still goes back whenever he can to the club – which is still celebrating his selection by Warren Gatland.
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Sinckler is yet to start a Test match for England but his impact at club level for Harlequins and off the bench under Eddie Jones has been colossal.
However, the front row monster was once 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 current Battersea first-team captain Marcus Bailey 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,” he said.
“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.
Kyle Sinckler was a bulldozing inside centre for Battersea Ironsides back in 2008
“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 tight-head prop and it is great to see.
“Our game plan 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.”
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Sinckler still retains a deep affection for the club, and Bailey admits they celebrated as much as he did when his name was read out last month.
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
Now he is gearing up for the biggest test of his career, but Bailey insists he will thrive under the pressure.
“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 said.
“That comes from his mum, his home and the club. I am sure he will add a bit of humour on Tour and pick the guys up if they are ever down.
“I was so chuffed for him. I literally jumped out of my chair. He was in a Quins team meeting so he did not actually know.
“I messaged him but did not get a reply for ages because he was sent about 1,000.
“I was so happy for him. Everyone at the club is so happy – there is a big banner up there now. So it is a real local success.”
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 brilliantly in attracting over 1,000 young players between six and 18.
It is now the largest junior club in the country, a far cry from where it started 22 years ago when three original founding members started coaching just 20.
It is still run on an entirely voluntary basis, and remarkably does not own a single rugby pitch – renting space from local schools and the council each week.
“Our location is really good. We have about 1,000 kids from the age of six to 18. It is crazy. We were at their fun day a couple of weeks ago and Kyle came down to it,” Bailey said.
“We had hundreds of children running round in all directions, it was crazy.
“Everyone has their own lives in south-west London. They are all in their own mind and are going about their own business.
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
“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.
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“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.”
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.
Kyle Sinckler – 2017
Kyle Sinckler was on hand to distribute the awards to this year’s Ironsides minis