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.

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.’
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].’

(Armani)