Jethro Compton (book and lyrics, director and stage designer): The Olivier awards were a huge boost for us. I wasn’t aware of the impact an Olivier win could have. We were already in conversations with different organisations around the world about getting the show out internationally – those have stepped up quite dramatically.

Philippa Hogg (actor, musician and creative associate): The ceremony was so much fun. We came on at the Royal Albert Hall to this roar from thousands of people.

Clare Foster (plays Elowen Keene): Our fans are incredible. One gave me this beautiful letter with a wooden box, which had a pickled crab design. It could belong on our set. I opened it and it was the Diary of Elowen.

Darren Clark (music and lyrics, co-music supervisor, orchestrator and arranger): There are generous souls working on this show – we talk about people who are “Button”. One of those qualities is an open heart; another is a curiosity about life.

John Dagleish (plays Benjamin Button): Any story that is very human works well through the lens of an absurd conceit, like a man ageing backwards. The message about making the most of the time you have is much more poignant with a life led the opposite way around because there is a finite number of years and a specific end date.

Philippa Hogg: Everyone on that stage feels connected to the themes, particularly being an outsider. It feels like a band of misfits telling the story of a misfit. Playing instruments and singing together is an ancient art form. You have to listen so hard when you play music and sing together and that ultimately connects people on a deeper level than just playing a scene. And this is very much a non-hierarchical piece – that’s quite rare.

Jethro Compton: There’s nothing like it in the West End. An actor-musician storytelling show is very different to what people are used to experiencing here. It would not have been developed this way if it had originated in the commercial sector instead of the fringe. Musicals are so expensive to develop that producers aren’t taking risks. This show has a title that people may have heard of from the film and short story but it’s created by a group of unknown people, pretty much. That’s part of its charm.

Clare Foster: Telling an entire lifespan on stage makes people reflect on their own lives. They leave wanting to call their mum or to hold their partner’s hand a bit tighter because it deals with the big stuff. When my friends come and watch, they don’t – spoiler alert! – cope with me dying very well.

John Dagleish: But Jethro has this phrase that he uses: “shitting on the romance”. Whenever anything becomes melodramatic or a bit too sepia, he pumps the brakes and throws in a little gag. It allows the audience a bit of respite from the heaviness.

Clare Foster: When I joined the company, Jethro talked so much about it as an ensemble show. That word can get thrown around a lot. But it really is an ensemble in its core. A cast of actor-musicians changes the dynamic of a company because there’s an inherent reliance on each other. It never feels like a particular person is singing a song with a band; it feels like a group of storytellers collaborating.

Darren Clark: There’s something in the show for everyone to reflect on. I wanted the music to feel like it was sort of rushing over you like a wave. There would be moments where you felt like you were inside a storm and others when the water was lapping at your toes.

Anna Kelsey (costume designer and associate stage designer): We wanted the set to feel like it was all falling into the ocean. The stage at the Ambassadors theatre is already raked. We added more of a rake, which does look great, but there was a lot of adjusting to it.

Philippa Hogg: We dropped a tankard and it rolled into someone’s lap in the front row! It takes some getting used to for the body, especially when you’re dancing, as your centre of gravity is a bit wonky. But it kind of gives that rickety pier feel.

Anna Kelsey: On some shows the pieces don’t all seem to come together. But with this one, they really did. We knew we wanted Benjamin to wear a suit and for it to feel like he was filling it out as as he gets younger. So at the beginning of the show, John is very hunched over and his jacket has been cut to be oversized. At one point, he changes it for one made of the same fabric but with a cut that fits him better. Then he changes his hair in the interval, too. It all helps the process without that transformation becoming the focus of the show.

John Dagleish: With Benjamin, we didn’t want to do a send-up caricature of an old man, a Julie Walters “two soups” kind of thing! We wanted to find something real that wasn’t based on makeup or prosthetics – something that would be believable without being too showy. So we discussed this idea of weight in his movement and a voice like I’ve been shouting all night, a shallowness of breath.

Anna Kelsey: We did talk about him having a moustache at the top of the show. We cut it because no character ageing normally through the show is aided by anything like that. Also finding a place where John could actually take it off was challenging!

John Dagleish: I’d forgotten about the moustache! It would have felt more like you’re doing a “bit”, rather than selling this as authentically as we could sell it.

Anna Kelsey: There was this idea that the swirling ensemble are called strangers. We talked about them being sort of washed up out of the ocean. The ensemble colours were timeless tones of the earth, sea and coast. But for the main characters I referenced items like life buoys, fishing floats, manmade colours of the coastline – so Benjamin’s got a bit of yellow, Elowen has orange.

Philippa Hogg: The mystical nature of Benjamin Button, and the folkloric way that we tell the story, has so much truth in it. Elowen sings the line “for a person can be old and yet be young”. We all have that childlike nature in us but then young children can have these moments of profound wisdom. You think: where the hell did that come from? If anything, the show has made me think the traditional concept of ageing is a load of rubbish.

John Dagleish: Benjamin is a very wise but naive character when he’s born. Jethro described it like, he’s already had all of the experiences but he just doesn’t remember them yet. So you’re playing this kind of childish naivety but with some sense of maturity and wisdom behind it as well. And then, as the younger man, I get to play it with a wealth of experience as well as an impetuous midlife crisis kind of vibe.

Jethro Compton: If you try to make the fact that he is born old in any way believable or realistic, it doesn’t work. I think the 2008 film version went wrong in that they made him baby-sized, so the whole thing is a bit weird. The more absurd we made it, the more we leaned into making it a fairytale, the quicker the audience could accept it and move on. Benjamin is born old and falls in love with a younger woman. But I was very conscious of not wanting it to be creepy or sinister.

Clare Foster: There’s something that’s a little bit ick about the concept but Jethro and Darren have done such a great job. I don’t think you ever really feel the ick!

Jethro Compton: Largely that comes down to the ages of the actors that we cast but also that Elowen is the driving force of the relationship. Benjamin is not pursuing her – she very much pursues him. She doesn’t care what age he may or may not be, she’s only interested in who he is as a person.

Clare Foster: The producer Richard Darbourne, who I did Guys and Dolls with 10 years ago, messaged me and said: you should come in for this. His text said: “High stakes, big heart, you eat that shit for breakfast!” It was one of those lovely rare auditions where, in the room, it just felt like the right fit.

Philippa Hogg: Before we go on stage we do a physical and vocal warmup then come together in a big circle, arms around each other. Anyone from the cast or crew then has the opportunity to dedicate that performance to someone or something they have experienced that makes them think of the show. So we have a focus for the next couple of hours.

John Dagleish: Jethro sent me some recordings of the earlier production and I fell in love with the music immediately. I remember the first day of rehearsal when I joined the company. What you would normally do is sit around a table and have a read-through. But we basically had a play-through with all of these amazing actor-musicians. Within the first two songs, everyone was in tears.

Darren Clark: I would say there’s probably between 10 and 15 songs that were cut over the years. We’d write a version of something, then take a little bit of that and write another one and so on. It’s like making whisky, it’s about distilling the idea. My life changed so much during the period of writing it. I became a father, I got married. A lot of the life that I have now is encapsulated within those years of making the show. I put the essence of my experience as a father into some of the lyrics.

Jethro Compton: We partnered with new producers for the West End. There were definite challenges in scaling up the show. We redeveloped it, with a new cast except for two of the company from when we did it at Southwark Playhouse.

Anna Kelsey: One of the challenges we had back then was how hot the actors got. We had a lot more layers of costume. Our coastal reference images included thick fishing jumpers which I love the look of but it’s so impractical as the actors were just on the move all the time.

Philippa Hogg: Before moving to Southwark Playhouse Elephant, we put it on at Southwark’s Little stage with a cast of five in 2019. I remember thinking: how the hell are we going to do this tastefully? For Benjamin’s entrance, there was a big creaky puppet made of driftwood that kind of flew apart into different pieces and then James Marlowe played Benjamin until the end when we had a child puppet made of buckets and bits of beach plastic. Benjamin and Little Jack didn’t go to sea in the earlier version; they went to the mines.

Anna Kelsey: We got loads of costumes from car boot fairs and charity shops. There was no time for anyone to leave the stage for a costume change, with all of the music to consider.

Darren Clark: Guitar is my home instrument. I knew that there would be lots of guitars with Celtic folk tunings. And fiddles, mandolin and the cello which feels like a human voice. There’s nothing quite like a solo cello playing something beautiful and mournful. And then I’d always had this vision of two sets of drums. I wanted to be able to capture vast and epic, as well as intimate and beautiful. That’s the way life operates: we have big moments and tiny moments.

Jethro Compton: We did a week of previews in Salisbury before we went to London. That original production was self-financed and self-produced – I built the set, drove the van, did too many jobs myself.

Philippa Hogg: For the first performances, we rehearsed in Cornwall. We had a couple of cottages in Bude. It really informed the feel of the show because every night we were on the beach. We had two actors playing Elowen. So I played her in part one, which takes you to the age of about 35, and then Rosalind Ford played her in part two.

Jethro Compton: We rented out a space above a bowling alley in Bude for a week. We put the whole set together, rehearsed it for a week, then did a first sharing. An invited dress rehearsal basically. A number of local people were there, including my father who played with a ukulele group beforehand then stayed to watch. The cast size was hugely different, but its heart was the same.

Darren Clark: It’s a deeply flawed short story but I saw the potential in it. Jethro added the tension of Benjamin trying to hide a secret.

Jethro Compton: Fitzgerald’s story is ultimately a fairytale. That folklorish quality fit really well with the world of a Cornish folk musical. I didn’t particularly enjoy reading the story – it’s very dated, cold. But I liked the fact that I didn’t like the story. In my experience, adapting something that you think is a bit flawed allows you more freedom because you’re not too respectful to the material. Sometimes you need to be unafraid to break it and make something new.

Darren Clark: When it was a show for five performers, often only two of those people were playing instruments in any number. That first version had spirit and soul, but it didn’t have the depth of the story we wanted to tell.

Philippa Hogg: I’d just worked with Darren on another show and in 2018 he asked me to record a demo for Benjamin Button. It was The Moon and the Sea. I was like, wow, something special is going on here.

Darren Clark: I had been rather badly burned by a previous project that made me want to test my collaborators before getting involved. So when Jethro sent me a lyric I restructured it entirely, set it to music and sent it back. I thought, if this guy can take this, then he’s the kind of guy I want to work with, because it’ll be all about the story. He came back almost immediately, added his own suggestions and the song grew even before we had officially signed a contract.

Jethro Compton: After making a lot of work set in America, I wanted to do something closer to home. I thought Cornwall would be a good setting but had never made a musical before … I was terrified about how to even begin!

• The Curious Case of Benjamin Button is at the Ambassadors theatre, London, and the cast recording is available to stream from 16 May