Now, Winston works with One Direction, JLS, David Beckham and Robbie Williams. And of course, as executive producer of The Late Late Show, he is the youngest show-runner on late-night television in America. But, for all his achievements, Winston clearly still sees himself as a nice Jewish boy from north-west London.
"I would not have ever seen my life going this way," he says. "But this stuff just happens. You follow a path and see where it leads you."
Winston is very easy to get on with, refreshingly open, and it's clear that it is his traditional background that has kept him grounded, a reflection of how his father, top scientist Lord Robert Winston, raised his family.
"When I was a child, I remember my father leaving the house at 6am and not getting home until midnight. We would rarely see him during the week because he was so busy but, on a Friday afternoon, he would always be home and stay all the way through Shabbat. That was a really lovely thing to grow up with - it was a really important factor in our childhood and I think that's a very important lesson."
Winston, who keeps a kosher home and does not drive on Shabbat, continues: "I do not think I keep the stuff I keep because I am incredibly God-fearing. It's just a way of life, how I have been brought up. Especially in LA, with all the people you work with and the shows you make, you can get very swept up and think it is the most important thing in the world, when actually the nice thing about Shabbat, however much you keep of it, is it adds something extra to your life. Judaism has been a huge part of my life and upbringing - and it is in my adult life too."
While so many high-profile figures seek to separate their personal from their professional life, Winston seems to have successfully managed to fuse the two.
Look closely and you can spot clues to Winston's background in his work. For example, watch the video for the One Direction single Midnight Memories and you will not only spot a London Lion player who he once coached, but behind Harry Styles, you will see a sign for ''Mashiach'' records store on the set. In one instalment of the Late Late Show, Corden took on the role of a kosher butcher, talking in Yiddish during the stunt.
Winston admits that bringing Jewish culture into showbiz can be easier than in the UK. "I am not saying you couldn't do something like that in the UK, but in LA and New York there's a huge Jewish culture - especially in the business that we are in. I would do something like that in the UK, but it might not have been as prominent."
But it has been a double-edged sword. Tabloid headlines have widely billed Winston as the man responsible for teaching those like One Direction's Styles Yiddish and Hebrew. They've insinuated that Styles has considered converting to Judaism at Winston's influence.
"There have been a lot of stupid articles," he says, irritated by the comment. "It's b******s, just not true. There is no indoctrination of the 1D boys becoming Jewish. It's absurd.
"I am a modern Orthodox guy who works in an industry with lots of non-Jewish people. You invite people over for a Friday night because they are your friends or colleagues. That is all it is."
It has not been a straightforward route to the top. Aged 18, he sat around his Friday-night table with his family a few months before he was set to go to Israel on a gap year. He had two offers on the table: spend the next few months on the set of a then unknown TV show in Bristol for no money or get a paid job working with his heroes, the Arsenal football team, with an agent ("and I'm an Arsenal nut").
The choice was simple. He told his family he would opt for the latter, before his elder sister Tania (now a documentary maker), "gave me what for. She said I was being pathetic for not wanting to leave home or challenge myself. To prove my sister wrong, I found myself on a cold train up to Bristol, to live in a place I had never been to and work for no money."
As a "general dogsbody", he met Corden on his first day on the set of Teachers. "We recognised sheer ambition in one another. We both knew we wanted to make it and make it quite big. We became the closest of friends. I never thought it would lead to working out in LA and making a show with him every day.
''I do think back a lot to that Friday night. You never know where things are going to lead you and sometimes it is about taking a bit of a risk. It is about doing something that you're not sure is going to work or doing the thing that steps you out of your comfort zone. But when it pays off, it pays off hugely."
When he was 23, he decided broadcasting was his destiny. After grappling for an initial £170,000 investment, he and his partners stumbled across their first hit. In The Hands of The Gods, which went on to be the widest release of a UK cinema documentary at the time, followed five British freestyle footballers to Argentina in a bid to meet Diego Maradona.
"We were straight out of university and didn't know what we were doing with our lives," he recalls. "We came across the kids and thought it was an incredible film to make. We were very typical ambitious kids thinking, we don't want to go to a production company, we want to own this and run it ourselves. So we formed our own production company. It was a crazy thing to do in a way. For two years, we dedicated ourselves to this film. We cut costs wherever we could. We didn't take a wage, we worked out of our bedrooms – we took a risk and it paid off. But we had very good people around us. We needed our parents to not pressure us to do something else – to not say: 'Shouldn't you try and be a lawyer?' My parents have been unbelievable."
Making fundraising films for communal organisations such as Magen David Adom to Jewish Care, Chai Cancer Care and World Jewish Relief from 2007-2009 were vital for Fulwell 73 . "They really kept us going - five grand here, ten grand there. We treated them like we were making a movie. To this day, even though we are making The Late Late Show, we are still making a lot of these Jewish charity films. Those films kept us going during the dry spells."
Winston says he likes to look ahead. So I wonder whether he, a Labourite (like his Labour peer father) who says he prays for the day that David Miliband "changes his mind and comes back to the Labour party – he would be the most phenomenal leader of our party", will turn to making political or religious films in future, or whether entertainment really is his shtick.
"For me personally, I'm a bit more corny and mainstream. My talents line in the Late Shows of this world, the Carpools and the X Factors.
"I am interested in popular culture - I guess I have got good at it."
And in response to all the anti-Israel boycott initiatives targeting show-business, Winston says: "Nothing would make me happier than for there to be a Carpool Karaoke spin-off in Israel with one of their pop stars. It would be tremendous."
He headed home on Wednesday to celebrate Pesach with his family. Next week, he will be speaking at a fundraising event for Maccabi GB and Young UJIA, describing his speedy rise to the top. Yet, for Winston, there's no place like home. "Los Angeles is a great place to be," he says. "It's not like they don't have a Jewish community, and people are very welcoming here.
"But it is very different for me. My friends and family are all in the UK. Community is often about the people you grew up with, who you know and love.
"I am here to challenge myself in my career but, for sure, my life and friends are in London and that community is very important to me.
"I don't know how long I am going to be in LA for, but I definitely see my home as London rather than here."
