The co-creator and co-director of “SIX: The Musical,” Lucy Moss, was in a cab on March 12, 2020, hours before her production was due to open on Broadway. The radio happened to be on, and she heard Governor Cuomo announcing that Broadway shows would shut down for several weeks due to Covid. 

Weeks turned to months, and Ms. Moss’s creative partner, Toby Marlow, began to worry after months turned into more than a year. “Everything was so uncertain,” he says. “Regardless of what the producers were saying, I thought, ‘Perhaps this is the end of theater as we know it.’”

Unlike the characters in “SIX” — the wives of Henry VIII, who compete in a pop-concert format to determine who had the most woeful experience with the tyrant — the production has enjoyed a happy ending. It opened in October to enthusiastic reviews, and has continued to build on the avid, largely youthful following the musical developed as a hit on London’s West End, where it opened in 2019 and is still running.

Young fans are not the show’s only admirers: “SIX” is up for eight Tony Awards this Sunday, including best musical and best score of a musical. Ms. Moss, who co-wrote the book, music, and lyrics with Mr. Marlow, is also nominated with Jamie Armitage for best direction of a musical.

That’s not a bad welcome for a pair of Brits who aren’t long out of Cambridge University, where Mr. Marlow, now 27, and Ms. Moss, 28, met as students. “SIX” was initially conceived when that prestigious institution’s musical theater society chose Mr. Moss to develop a project for the Edinburgh Festival Fringe, where the show was first staged in 2017.

Growing up, Mr. Marlow was “a massive, massive pop nerd. I had Gaga and Beyoncé posters lining my walls.” Although also a fan of Andrew Lloyd Webber musicals such as “Joseph and the Amazing Technicolor Dreamcoat” and “Cats,” he notes, “I really became more of a musical theater buff when I got involved in the society, because a lot of my friends had this encyclopedic knowledge.”

Mr. Marlow’s proposal for Edinburgh involved “writing something that could have a majority of female or non-binary cast members and famous subject matter, and use pop music, which is what I like to write. I thought, ‘What’s a good group of women from history or fiction?’” After choosing the Tudor queens and determining that a concert format would work, he contacted Ms. Moss, who conveniently happened to be a history major.

As it turns out, Ms. Moss muses, “I had a very specific interest in writing revisionist things about that time period. It was so random that we just happened to have the exact skill set we needed for this show.”

A positive reception at Edinburgh led to a professional production that toured the U.K. Several months after its West End opening, “SIX” kicked off a North American tour in Chicago. The show is also being staged in Australia and New Zealand, and a second U.S. tour is scheduled to begin in Las Vegas in September.

These productions have included several cast members who identify as non-binary in terms of gender. Mr. Moss, who answers to the pronouns “they” and “them” as well as “he” and “him” — “I basically haven’t settled on a singular term that fully encapsulates my experience or gender,” he explains — actually stepped into the role of Catherine Parr, Henry’s final wife, for a couple of West End performances in 2019.

Ms. Moss notes that the first actor to play Henry’s fourth wife, Ana of Cleves, “is non-binary, and helped open my eyes to the way we were gendering a lot of the language. When we started writing the show, to be honest, my understanding of gender and non-binary identity was much more limited. So in the first draft, it was, ‘Ladies and gentlemen, how are you doing?’ We had to learn to be more inclusive.”

Bringing “SIX” across the pond led to other revelations. “Something we realized in Chicago is that Americans know how to be good, loud, responsive audiences. I remember at our first preview, I was thinking, ‘Oh God, are they going to get it? Will the show work here?’ And then the second the lights came down and the queens walked onstage, there was this roar — it was absolutely wild.”

Mr. Marlow, who is developing other projects with Ms. Moss — among them a musical comedy called “Why Am I So Single,” and a television series in which he’ll also appear — notes that in preparing “SIX” for London, “We had lines like, ‘How’s everyone doing tonight? Make some noise!’ That’s completely redundant in New York, because the minute anyone does anything, they start cheering and screaming. It really is like being at a concert, and it’s wonderful.”