As he walked on stage in front of 92,000 screaming Taylor Swift fans last night, Jack Antonoff cut a rather unassuming figure.

Dressed in a navy t-shirt and baggy black trousers, the average person could have easily mistaken the 40-year-old for a member of the crew at London‘s Wembley stadium.

But as Taylor Swift superfans will know, the music producer is the brains behind some of the pop star’s greatest hits – including Anti-Hero, Cruel Summer, August, Bejeweled and I Can Do It With a Broken Heart.

As she began the acoustic set for her final European Eras Tour show, Taylor, 34, teased fans how ‘one of her best friends in the world’ in the crowd – before Jack emerged from below the stage.

Much to the delight of the Wembley crowd (and hundreds of thousands of fans tuning in via live streams around the world), the duo performed their 2017 hit Getaway Car, which was mashed up with Death by a Thousand Cuts from the 2019 Lover album.

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Pictured: Taylor Swift was joined by Jack Antonoff on stage at Wembley last night for the last Eras Tour concert in the European leg

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Jack Antonoff was a producer on Taylor Swift’s 2020 album Folklore, which won multiple Grammys

What’s more, the producer’s love life has proven to be equally as noteworthy – as he previously dated Scarlett Johansson and Lena Dunham before marrying Margaret Qualley, who is the daughter of Andie MacDowell, last year.

So how did this songwriter from New Jersey go from performing in a little-known indie band to collaborating on some of the most commercially successful songs of the 21st century?

Here FEMAIL delves into Jack Antonoff’s professional and personal life – as he becomes the latest surprise guest on the Eras Tour.

Devastating loss of sister as a teen

Jack Antonoff was born in March 1984 in Bergenfield, New Jersey, and was one of Rick and Shira Antonoff’s three children.

The producer joined his band – named ‘Outline’ – when he was a sophomore in high school and released their first EP through a friend’s record label. The band even embarked on a tour of Florida and Texas when Jack was only 15.

When he was 18, Jack lost his younger sister Sarah to brain cancer and has previously spoken about his regret over spending her final years largely on tour.

In 2017, he told People: ‘[My life] is very much a then versus now. For me, it’s 18 and younger, when my sister was alive.’

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Pictured: Jack Antonoff playing guitar as a teenager. The songwriter and producer joined his first band when he was 15

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Pictured: Jack Antonoff as a child with his parents Rick and Shira and his sisters Rachel and Sarah, who died of brain cancer at 13

The devastating loss left Jack battling anxiety and trapped in a ‘worst-case-scenario’ way of thinking.

Speaking to Billboard magazine in 2014, Jack explained: ‘I go down this rabbit hole with the way I’m wired, and it can make life very unenjoyable. So I try to stop myself as much as I can.’

At the time of Sarah’s death, Jack was touring with his second band Steel Train and turned to drugs to escape his grief.

In an interview with Apple Music, the producer recalled how he would get ‘really f***ed up’ on pills with friends – but never realised how dangerous they could be.

After his sister’s passing, Jack explained: ‘We were touring a lot and I was obviously just so f***ed up emotionally that I took a whole bunch of mushrooms one night with some friends and I completely freaked out. I completely lost my mind.

‘And I think it was a combination of how much I took and the grief and the long story short is I was so f—ed up from that experience that to this day I feel allergic [to drugs].’

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Jack Antonoff was born in March 1984 in Bergenfield, New Jersey, and was one of Rick and Shira Antonoff’s three children

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Pictured: Jack Antonoff in December 2021. At the time of Sarah’s death, Jack was touring with his second band Steel Train and turned to drugs to escape his grief

As such, Jack says he has never wanted to ‘be out of control again’ and will only have a ‘drink or two’ as a result.

The star also said song-writing helped him process the profound loss and told People magazine how it makes him ‘feel less alone’.

As a young man, Jack set his sights on leaving New Jersey and making a name for himself in music.

He told Billboard: ‘There was this darkness about being from New Jersey. We’re in the shadow of the greatest place in the world, New York City.’

Speaking to NPR, the producer added: ‘All I wanted to do was break out, I wanted to go everywhere and do everything and tour the world and, you know, make my mark. And that slow, slow, slow boredom of where I grew up made my imagination run wild.’

High-profile love life (including high school romance with Scarlett Johansson!)

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Pictured: Jack Antonoff with his high school sweetheart Scarlett Johansson at a fashion show in September 2002

When he was still a high school student, Jack Antonoff dated a classmate, who would turn out to have even more success on the world stage than him.

His first known girlfriend was Scarlett Johansson – who also attended the Professional Children’s School on the Manhattan’s Upper West Side.

The pair attended prom together in 2002 and were pictured at the BCBG Spring 2003 fashion show at New York Fashion Week the following year.

‘When we were in high school, Jack was absolutely obsessed with her, and she broke his heart,’ a friend of the guitarist told the New York Post. ‘They broke up shortly after graduation. She got swept up in the Hollywood scene.’

Scarlett already had a few big-time gigs by then, too, in Home Alone 3, The Horse Whisperer, and The Man Who Wasn’t There.

In February 2014, Jack’s then-girlfriend Lena Dunham admitted she thought she was ‘hallucinating’ when she stumbled upon photos of him and Scarlett on Tumblr.

She said: ‘I’m not jealous. It’s very sweet. I love looking at pictures of them.’

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Pictured: Jack Antonoff’s rumoured ex-girlfriend Alia Shawkat, whom he is believed to have dated for a year in 2009

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Pictured: Jack Antonoff with ex-girlfriend and Girls creator Lena Dunham, whom he dated from 2012-2018

In 2009, Jack was reported to be dating Arrested Development Alia Shawkat – and the pair are believed to have been in a relationship for a year.

However, Jack and Alia have never publicly commented on the rumours and the actress – who is starring in Zoe Kravitz’s upcoming film Blink Twice – even appeared in the music video for Bleachers’ Don’t Take the Money in 2017.

In 2012, Jack began dating Lena Dunham, who was directing and starring in the hugely successful HBO series Girls.

In an interview with Vulture, Jack revealed they were set up on a blind date shortly after Girls first aired.

He said of their first meeting: ‘I told Lena everything about my whole life, because when you really like someone, you want them to know everything about you.’

Meanwhile, Lena told Glamour that she appreciated Jack calling the internet discourse around the nudity in Girls ‘bulls***’.

At the time, Jack said they were a ‘good match’ as neither of them liked partying and detailed how they were the only ones not invited to smoke marijuana at a dinner party they attended with couples in their 60s. He joked: ‘That basically says it all.’

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In 2012, Jack began dating Lena Dunham (pictured in 2015), who was directing and starring in the hugely successful HBO series Girls

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Jack (pictured in 2014) said of his first meeting with his ex: ‘I told Lena everything about my whole life, because when you really like someone, you want them to know everything about you’

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Speaking to The Guardian in 2014, Lena said of Jack: ‘I’ve had boyfriends before, but never someone who was a constructive member of society and made my life better.

‘And I have a really great boyfriend now. I’m really lucky. It would be hard to be with someone who wasn’t supportive of what I did.’

Two years into their relationship, the couple moved into a house in Brooklyn Heights and were known as one of the strongest romances in Hollywood.

How Taylor Swift ‘changed his life’ 

Not only was 2012 the year Jack first started dating Lena – but it’s also when he began working with Taylor Swift.

The pair are reported to have met at the MTV European Music Awards in November and bonded over their love of the 1982 Yazoo song Only You.

At the time, Jack was best known for writing his band fun.’s song We Are Young, which went to number one in the US, UK, Australia, Canada, Ireland, Mexico, Poland and Iceland.

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Pictured: Laura Sisk, Jack Antonoff, Taylor Swift, Aaron Dessner, and Jonathan Low during the recording of Folklore

The following year, Taylor and Jack collaborated on the song Sweeter than Fiction, which appeared on the soundtrack for the movie One Chance about Britain’s Got Talent winner Paul Potts.

In 2014, Taylor asked Jack to help produce her album 1989 – with him later gushing on Instagram: ‘Will one day write an essay on the different production I used on the song + how much working with Taylor on it has meant to me. She’s a wonderful artist.’

While promoting the album, Taylor revealed in an interview with ELLE magazine that the song You Are in Love was inspired by Jack and Lena’s relationship and how they were each other’s best friends.

The star said: ‘I think that that kind of relationship — God, it sounds like it would just be so beautiful — would also be hard. It would also be mundane at times.’

Since 2012, Jack has won 11 Grammy Awards – including three Album of the Years for Taylor Swift’s 1989, Folklore and Midnights and three Producer of the Year awards.

Following their Folklore win in 2020, Jack addressed Taylor on Instagram and wrote: ‘You are the one who let me produce records first.

‘Before you, I just “wasn’t a producer” according to the herbs. I just wasn’t let in that room. Then I met you, we made out of the woods and you said, “that’s the version” and that changed my life right there.’

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Pictured: Jack Antonoff with Taylor Swift and Lana del Rey at the 66th Grammy Awards in February 2024

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Much to the delight of the Wembley crowd, the duo (pictured) performed their 2017 hit Getaway Car last night, which was mashed up with Death by a Thousand Cuts from the 2019 Lover album

In 2019, he also won a Grammy for Song of the Year and Album of the Year for Lana del Rey’s Norman F***ing Rockwell, which he produced.

In March 2024, Jack opened up about his working relationship with Taylor and told the Evening Standard: ‘I think when something is so brilliant, it freaks people out.’

Lena break-up and Lorde cheating rumours

In 2018, Lena Dunham wrote a powerful personal essay for Vogue where she revealed she had undergone a hysterectomy to alleviate the symptoms of her endometriosis.

Opening up about the impact the chronic condition had had on her relationship, Lena explained: ‘My beautiful partner, who has seen me through so much pain with compassion and care, has to be away for work, and I can feel us growing slowly apart, since life is so determined to display its full complexity right now.

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Around the time of Jack and Lena’s split in 2018, Jack and Lorde were plagued by rumours they’d had an affair – which the singer has denied

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Pictured: Jack Antonoff’s ex-girlfriend Lena Dunham with Lorde at the Pre-GRAMMY Gala in February 2017

‘I am surly and distant. I offer nothing. He reminds me again and again that I am still a woman and still alive, but I also know that soon—for so many reasons that have nothing to do with my uterus—we’ll slip away from each other and I will face everything I am losing in impossibly tiny steps.’

In an essay for Domino in 2019, Lena revealed the heart wrenching comment Jack made during their final conversation as a couple.

She wrote: ‘”You can finally eat in the bed without anyone getting mad at you,” he said through tears. ‘

Around the time of their break-up, Jack Antonoff was plagued with rumours by fans that he had cheated on Lena with Lorde – an allegation the musician has always strenuously denied.

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Lorde (pictured in 2018) also told Ash London on Australia’s Hit Network she sees Jack as a ‘platonic husband’

Speaking to the New York Times in 2021, the songstress hit back at the ‘growing narrative’ concerning her connection to Jack following his involvement in her new album Solar Power.

Lorde, whose real name is Ella Marija Lani Yelich-O’Connor, said it was ‘insulting’ and ‘sexist’ for critics to refer to Solar Power as ‘a Jack Antonoff record’.

She also told Ash London on Australia’s Hit Network she sees Jack as a ‘platonic husband’.

Lorde said: ‘Jack’s and my relationship is really deep and is like a marriage in some ways – a platonic marriage.

‘We’re in it for life I think at this point. We’ve been very close for five or six years now. We don’t seem to get sick of each other. But who knows, anything could happen.’

Love at first sight with Margaret Qualley

Pictured: Jack Antonoff with wife Margaret Qualley, who is the daughter of Andie MacDowell, at the 27th Annual Critics Choice Awards in March 2022

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Lana del Rey detailed the couple’s first meeting in her 2023 song Margaret, which stated they connected at a rooftop party

In 2021, Jack’s life changed forever when he met Margaret Qualley – who was best known for her role in the Netflix series Maid.

Lana del Rey detailed the couple’s first meeting in her 2023 song Margaret, which stated they connected at a rooftop party.

The producer is described as ‘having flashes of the good life’ and quoted telling Lana: ‘I might be in trouble. Should I jump off this building now or do it on the double?’

In a February 2024 interview with Elle UK, Margaret said that she experienced love at first sight with her now husband.

She said: ‘I’d met Jack probably two weeks before, but I was head-over-heels in love right away. I had a sure, knowing feeling that he was my husband.’

Recalling the moment and her nuptials prediction during the fashion show, which brought a big beaming smile to her face, the actress just happened to be getting fitted to wear an ivory wedding gown at the time.

‘I was talking about Jack and said to her, “I think I’ve just met a man I’m going to marry. And, Virginie, if I’m right, will you make me my wedding dress?” I said, ‘Give me two years…”’

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In 2021, Jack’s life changed forever when he met Margaret Qualley (pictured) – who was best known for her role in the Netflix series Maid

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Actress Margaret Qualley, 29, revealed that she knew she would marry music producer Jack Antonoff, 39, within two years after meeting him in the summer of 2021

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Some would call it the power of creative visualization, but Qualley did in fact marry Antonoff almost two years to the day that she made the confession to Viard during the Chanel haute couture show in 2021; the couple are pictured at their wedding in New Jersey in August 2023

Keeping to her word, Qualley and Antonoff did in fact get married on August 19, 2023, which was almost exactly two years to the day that she made her profound prediction.

It turned into a star-studded affair in New Jersey, where the bride wore a Chanel halter-neck gown, of course, Mary Jane shoes, and her dark locks was styled in a short bob.

The celebrity guest list included such A-listers as Taylor Swift, Channing Tatum, Lana Del Rey, Zoe Kravitiz, Cara Delevingne, Alex Wolff and Andie MacDowell, who just happened to be the bride’s famous mother.

In fact, the buzz about all the celebrity chatter quickly spread and eventually the road outside the Long Beach Island venue had to be shut down due to the growing crowd of fans that had gathered all trying to get a glimpse of the newlyweds and VIPs.

And in another case of the power of creative visualization, their wedding ended up being a big celebration full of their closest family and friends.

‘I’ve always wanted to be married,’ she explained, before recalling moments when she was a young girl. ‘I was that girly girl who would be on a walk with my sister fantasizing about our weddings, or what our husbands would be like.’

The Upon A Time In Hollywood star then admitted that she didn’t think it would have been a large wedding if it wasn’t for her husband, who was all down for a big celebration.

‘I wanted it to be big with him. It was, kind of, Jack needs a big wedding. And it seemed like it’d be more fun. He’s got so many great friends and a huge family, too. I think [weddings] are almost as much for your family and your friends as it is for you,’ she added, noting that it was ‘sweet and special and just the most magical day of my life.’