It’s a long way from the grey skies of Lancashire to the glitz and flashbulbs of the global fashion event of the year, the Gala at New York’s Metropolitan Museum. But when the world’s A-list fashionistas step out on its red carpet in a week’s time, they’ll be linked by an invisible thread to the mill town of Blackburn in the 1970s – and a Catholic schoolboy whose adolescence there was filled with the drama, the theatre and most of all the costumes of the church services at which he found himself.

That boy grew up to be the curator in chief of the Costume Institute at the Met. His name is Andrew Bolton, and today he’s one of the most influential, if low-key, figures in the world of fashion. His is the brain behind the theme for both the Met Gala and the accompanying costume exhibition which opens three days later – and it all links to his upbringing, his education and his childhood faith.

Heavenly Bodies: Fashion and the Catholic Imagination will explore the links between Catholic imagery and the creation of couture design; themes which Bolton says have never been properly explored on this scale, and which could help lift the costume galleries of the Met and other museums round the world out of their second-class silos forever. It will connect works of ecclesiastical art in the Met directly to couture, as a series of interventions: the Byzantine galleries will feature fashions inspired by church interiors, the medieval sculpture hall will look at fashions paired to holy orders, while the Met’s second site, the Cloisters – suitably enough, since it is a reconstruction of a medieval monastery – features designers inspired by monastic orders. Also on show will be more than 50 vestments borrowed from the Sistine Chapel collection, many of which have never previously left the Vatican. They will be shown in a separate space from the fashion, says Bolton, to preserve the sense of sacred – some are still used during services.

Being raised Catholic and immersed in it, has fired the imaginations of many designers

For Bolton – tall, lean and owlish in dark-rimmed glasses – it’s hard to overestimate the importance of this exhibition in his already stellar career. “It’s the show I’ve always wanted to do. It’s all about the influence of Catholicism on designers, about the links between the church’s imagery and creativity. Being raised Catholic, being immersed in this tradition, has fired the imaginations of so many designers.” It is, he says, the narrative impulses of the designers that are the deepest and most profound expressions of their Catholic imaginations: and while the high-octane fashions that are featured in the show might seem a long way from the sanctity of the church, he believes they embody its storytelling tradition.

Bolton’s thinking of luminaries including the Spanish Cristóbal Balenciaga (1895-1972) – “He was probably the most devout; he thought seriously about becoming a priest” – and the Italian surrealist Elsa Schiaparelli (1890-1973), who was baptised in St Peter’s Basilica. They both feature in the show, Schiaparelli with her evening dress of 1939 embroidered with the “keys of the kingdom” given by Christ to St Peter; Balenciaga with his sleek wedding dress of 1967, making his bride nun-like in its simplicity and wing-like veil. Then there’s Gianni Versace (his sister Donatella, along with Anna Wintour, Amal Clooney and Rihanna, are the official hosts for this year’s Met Gala), whose gold evening dress of 1997 is emblazoned with a cross that runs from collar to hem and breast to breast. Jean Paul Gaultier, another Catholic, is represented by a dress from his heavily religious spring/summer 2007 collection, inspired by stained glass and with an image of Christ à la Madonna and Child nestled across one shoulder; Dolce & Gabbana, by pieces from their autumn 2013 collection, which featured saints in a heavily jewelled print inspired by the Byzantine mosaics in Sicily’s Monreale Cathedral.

Holy trinities: Donatella Versace, Anna Wintour and Cardinal Gianfranco Ravasi. Photograph: Courtesy of The Metropolitan Museum of Art/@sgpitalia

The more he looked for church-inspired fashion, says Bolton, the more he found. From the House of Chanel’s 2008 collection there’s a jewelled gilet that looks like a collection of Rosary crucifixes, and Coco herself, he discovered, always carried a prayer-card of St Thérèse. Perhaps the most Pope-like outfit of all is a John Galliano evening dress from his autumn/winter collection 2000. It is full-length cream and gold with jewels and a mitre. Other designers represented in the show, also raised Catholics, include Jeanne Lanvin, Christian Lacroix – and Bolton’s own partner Thom Browne, one of Michelle Obama’s favourite designers (she wore a Browne coat-dress for her husband’s second inauguration day).

When I meet Bolton, at the press launch for Heavenly Bodies, Browne is also in attendance, wearing one of the short suits (fitted blazer with trousers cut off above the knee) that are his signature item. The event, held at a palazzo in central Rome, is swirling with stylish celebrities and top-level clerics. Donatella is there, wearing one of her own-label designs in strong block colours, while Wintour, after whom the space of the Met that houses the costume institute is named, is resplendent in a sumptuous, long velvet dress in cardinal red. Wintour almost upstages – but thankfully only almost – the real-life cardinal who is there to give the event the Vatican’s seal of approval, Gianfranco Ravasi, the head of the Pope’s culture department. Ravasi’s scarlet robes are, he says, the dress-down version of a top prelate’s wardrobe, certainly compared with the intricately embroidered copes and jewelled mitres that will be on display at the Met for Heavenly Bodies.

In this company, Bolton is understated. He’s wearing a dark suit that’s unremarkable save for the ankle-length trousers, another Browne signature. Those, together with his slightly foppish side-fringe, give him, at 51, an air of endearing boyishness. In Rome, as in New York, his Englishness singles him out, as does that of Wintour, with whom he works closely. But Bolton is a lot warmer than the famously icy Wintour. He’s easy to chat with and seems slightly out of place in this see-and-be-seen world. He is someone whose passions got him to where he is, rather than any desire to be noticed. Bolton says he didn’t think about becoming a priest, but it’s clear he considers what he does as a vocation. And what it all comes down to, he says, is telling stories – and more than that, allowing the objects to tell their own stories.

“That’s very much what I believe in,” he says. “I don’t see objects as being passive. Sometimes I think curators overload an object with interpretation. I want the object to tell its own story.”

Bolton’s most spectacular opportunity to let objects tell their own story came in 2011, when he staged the show that gave him his curatorial crown, Savage Beauty – the seismic, game-changing exhibition of the work of Alexander McQueen. Consisting almost entirely of exhibits, with barely any biographical information or background about the complicated life of their creator, whose early life was marred by sexual abuse, it took visitors on an emotional as well as a visual rollercoaster through the most spellbinding costumes created by the man known as the enfant terrible of British fashion. There was a razor clam seashell dress; a skirt made of plywood; a gold feathered dress; a headdress of dozens of bright red butterflies…

Designer couple: Andrew Bolton and Thom Browne. Photograph: Dave Benett/Getty Images

The show was a sensation and the Met was swamped. There were five-hour queues for entry, and for the first time the museum stayed open until midnight to cope. All this took the institution entirely by surprise because, as his predecessor at the Costume Institute, Harold Koda, often said, and Bolton is fond of quoting: “The Costume Institute is like the Met’s pretty little sister. It gets all the dates but none of the respect.”

But that is changing under Bolton – and how. He says he hates the word “blockbuster”, but there’s no doubt that’s what’s in everyone’s mind for Heavenly Bodies, which will be the biggest exhibition ever mounted at the Met, encompassing 25 galleries in all, and linking the two Met sites for a show for the first time. It will be, says Bolton, “like a pilgrimage… visitors will make the journey from one site to the other”. He hopes to take the art world on a journey, too, from the outdated view that costume galleries were fusty old second-class areas of museums located in basements, to a new dawn in which they are given what he would see as their rightful place alongside the paintings and objects that have always been regarded as artistic heritage. Linking costume with Catholicism, the faith that inspired the Renaissance, is clearly and unashamedly a step in that direction. “What you’ll see,” he says, “is fashion, art and religion intertwined.”

Religious dress and fashion are not distinct entities, both operate as a visual language

Bolton’s exhibitions – last year’s centred on the Japanese designer Rei Kawakubo, founder of Comme des Garçons; the previous year’s was Manus x Machina: Fashion in an Age of Technology; before that, China: Through the Looking Glass – always have a strong personal pull for him, and he called Savage Beauty “an unapologetic love poem to McQueen”. Just like McQueen, who never flinched from confronting difficulties in his own life through his art, Bolton doesn’t shy of bold, controversial decisions. He first mooted the idea of Savage Beauty with the then director of the Met, Thomas Campbell, the day after McQueen’s suicide. The show was staged barely a year later. Some said it was too soon. Bolton understood the power of the tragedy, the impact of the moment.

Heavenly Bodies won’t be without its critics, as Bolton is well aware. There will be traditional Catholics who won’t like the idea of working vestments being displayed as museum exhibits and who may feel the exhibition trivialises their faith, and liberal Catholics who will eschew the messages of hierarchy and rank and privilege inherent in items that are intricately decorated at great cost, both financial and in terms of time (one piece, says Bolton, took 15 women 15 years to complete). But while some will dislike the reminder of how elite top-ranking Catholic clerics have traditionally been, and others will argue that Pope Francis is steering Catholicism away from the kind of church that required opulent and lavish costumes, it’s undeniable that the costumes of the intricate, majestic and often downright camp liturgies of the Catholic church link in a very vivid way to the world of designer fashion.

And while Pope Francis may eschew papal pomp, preferring a Fiat to a limo (until as recently as 1978, popes were carried on a ceremonial throne called the gestatorial chair – it was replaced, by John Paul II, by the mechanised Popemobile), he is well aware of the power of symbolic costume. He’s never seen in anything other than a dove-white cassock or a chasuble and, unlike his predecessor Benedict XVI, he doesn’t bother with the traditional red designer loafers. For Bolton, “religious dress and fashion are not distinct entities… both operate as a visual language relying on subtle visual codes to perform specific functions and to explain complex ideas and identity.”

Renaissance fashion: Dolce & Gabbana’s 2013 collection. Photograph: Elliott Neep/Jason Lloyd-Evans

The Sistine Chapel loans for the show include the golden cope of Pope Benedict XV (who reigned from 1914 to 1922), the chasuble and mitre of his successor Pius XI and the 19th-century dalmatic of Pius IX, which features a scene from the crucifixion, as well as his heavily jewelled tiara. And while Pope Benedict’s famous red loafers won’t be on show, those of his predecessor John Paul II will be. It all underlines, says Bolton, the fact that the finest costumes in history were always either imperial or ecclesiastical. “There’s the secular court, and there’s the court of the church. And there was a very fluid relationship in the Middle Ages between elite culture and fashion. Catholic church leaders were very much the elite of those times.”

What’s also interesting, he says, is that fashions designed for male churchmen have been adapted for what are largely women’s outfits. That’s especially significant given that one of the reasons costume galleries have traditionally been given second-class status is because they’re seen as mostly connected with women and their lives. But most of all, and magically, there’s the overriding sense of mystery and awe and wonder, the transportation literally to another world, that links both the garb of the church and the world of designer fashion. No wonder, he says, that a fashion show seems almost like a religious ceremony. “Have you ever thought of the parallels there? There are active participants and passive participants, there’s music, there’s a procession…”

Originally, Heavenly Bodies was conceived as an exhibition exploring the influence on fashion of all five major religious traditions. “But as time went on we realised there was a huge imbalance between designers who were from the Catholic tradition, and those from the other faiths,” says Bolton. What that’s about, he believes, is a complex cocktail of ingredients that unite in Catholicism to fire up and liberate artistic creativity. “There’s the idea of storytelling, and there’s also the visual culture, which is fascinating and colourful.”

Bolton owes his own front seat on this complicated world mostly to his time at St Mary’s College in Blackburn. He went there at 16 and at that moment, he says, “my education really started”. Raised in a middle-class family, one of three children – his father was in publishing, his mother a nurse – he says his parents’ ambitions were orthodox. “They were thinking in terms of us being lawyers and doctors,” he says. But he was in the choir at school and loved it, and he always enjoyed the theatre of mass. He went on to study anthropology at UEA and stayed on as a postgraduate. “But what stopped me was realising I would never be as good as the good guys. I was too bourgeois to be an anthropologist.”

High order: Christian Lacroix’s 2009 show. Photograph: Pierre Verdy/AFP/Getty Images

One day a paper fell out of a book he was holding, and it turned out to be an application form for a job as curatorial assistant at the V&A. From the moment he got the job, he’s never looked back. Arriving there felt, he says, like going home. But it was his move nine years later, in 2002, to the Met that brought him to the forefront of the international gallery and fashion scene. He joined as associate curator, and since 2016 and Harold Koda’s retirement, he has been the Wendy Yu Curator in Charge of the Costume Institute.

In his private life, meanwhile, he and Browne have been together for the past seven years – presumably they wholeheartedly approve of the most famous quote of Pope Francis’s pontificate, which is his admission “Who am I to judge?” when questioned about homosexuality. The couple live in Manhattan with their dachshund, Hector, who they’re both devoted to.

As the critics gear up for the opening of Heavenly Bodies, and the fashion world prepares to be wowed by a series of priestly themed outfits on the red carpet, Bolton’s hope must be that with this show he will hit the same jackpot as with Savage Beauty, to which everything he ever does is invariably compared. He believes that what he has to say about the links between church and fashion are transformational – and if he ever says a prayer to the God of his childhood, here’s betting he’ll be saying one now.

Heavenly Bodies runs from 10 May to 8 October at the Metropolitan Museum of Art, New York (metmuseum.org)