Former New Zealand Prime Minister Dame Jacinda Ardern has penned a candid letter to her younger self, published in a British street paper.

In the revealing dispatch featured in the Big Issue, often sold on street corners by the homeless, the 45-year-old reflects on growing up as a “very earnest” young Mormon in Waikato and her meteoric rise in global politics.

Being raised in the Church of Jesus Christ of Latter-day Saints, Ardern said she felt a “huge burden of responsibility” and was often the only Mormon her friendship group knew.

“I was the sober driver,” she writes.

Ardern feels she had a typical Kiwi upbringing, listening to Metallica, Rage Against the Machine, Sepultura, Tool, Smashing Pumpkins and Violent Femmes, with a pet lamb and motorbike and learning to drive a tractor before a car.

“So it felt like I had lots of freedom,” she wrote in the Big Issue letter.

“I always hated injustice. It might be small or large things, but if I saw injustice, just knowing about it created an obligation. I was part of a group that belonged to Amnesty International. We would write letters about prisoners of conscience. When I was a kid, I did the 40-Hour Famine. And my church was involved in service activities. I felt that drive early on.

“In the 1980s, we were living in a town going through severe economic disruption. I remember seeing the impact of poverty on kids. We left when I was 8, but it absolutely politicised me, although at the time, it’s not how I would have identified it. I saw it through the lens of injustice."

Ardern says she would tell her younger self “don’t let anyone trivialise how you feel”, saying: “No teenager ever had it easy, but it is exponentially harder now.”

Former Prime Minister Dame Jacinda Ardern. Photo / Jane Ussher

“Imposter syndrome is very common – we just don’t talk about it,” she wrote in the Big Issue.

“Because the moment we confess to it, we think people will lack faith that we can do a job. I’ve got nothing to lose by talking about it now. So I talk about what it brings you. Because it brings you traits that are valuable in leadership. If you think you might not have what it takes, you’re going to research, prepare and bring humility to the role. You’ll bring in experts and advisers. And you will listen. Once you’ve gone through that process, you become decisive because you know the issue. And aren’t those things that we want in leadership?”

On her rise through the Labour Party ranks, she talked about wanting to bring kindness to politics, saying it should be a core value for all politicians.

Ardern wouldn’t want to talk to her younger self about relationships, though, talking about how she got together with Clarke Gayford at 34, so “the only thing I would say is relax. What will be, will be”.

Dame Jacinda Ardern and Clarke Gayford pictured at their wedding. Photo / Felicity Jean Photography

Prime Minister, the film chronicling Ardern’s tenure as New Zealand’s 40th Prime Minister, opens in UK cinemas on December 5.

The 102-minute film, which presents an account of her political and personal life over five years, covering crises such as the Christchurch mosque attack, the Whakaari-White Island volcanic eruption and the Covid-19 pandemic, has proved a box office success since it premiered at the Sundance Film Festival.

Ardern told the Herald in June 2024 that she supported the film because the producers had not sought Film Commission funding.

During an interview at the Sundance Film Festival, she said she cried when watching the final cut of the film.

“I was very emotional watching it. I credit the storytellers for it. I hoped that the film would humanise politicians, those who are public servants, and leadership, but I never thought it would humanise me. When I watched it, I just saw myself as someone who was trying to do their best.”