Come Alive: behind the scenes of London's new Greatest Showman experience

The circus is coming to town, but not as you know it. In February, when the BBC Earth Experience closed, it left a huge empty building in Earls Court . Eight months later, it's now The Empress Museum, home to new immersive experience Come Alive, in which the hit songs from The Greatest Showman are woven into a new story amid an extraordinary range of circus acts.

Released in 2017, the film became an unexpected hit, grossing half a billion dollars on a budget of $84 million. But what really stood out were the songs by Benj Pasek and Justin Paul: who hasn't heard someone wail This Is Me during a karaoke session several cocktails deep?

Now creative director Simon Hammerstein, best known as the founder of the very adult, very elite nightclub The Box in New York and Soho, has turned family-friendly. "It hasn't been easy," he says as opening night approaches, three dozen performers perfect their acts and preview audiences set social media alight with early glimpses of the show, "but going through the agony is the only way these things happen."

Skip to the beginning of 2024 and finally the project started to get off the ground. "We didn't have a venue or a story," Hammerstein recalls, "but we did have a tremendous amount of luck. The BBC Earth experience closed and the building was perfect."

The remit, he says, was to take Pasek and Paul's songs and come up with new characters and story. "I didn't sleep for months. It just existed in my dreams – how does this song make sense, if I put this song here that one has to go later... and staying true to certain tenets of each art form: what makes it circus as opposed to cabaret, what qualifies a musical as opposed to a concert?"

"We needed the building to have an identity," explains set designer Ruby Law, "so after a lot of iterations we settled on the idea of a museum. When you first come in, you see a big glass box with the iconic showman outfit inside. Then you walk through the Wall of Fame seeing pictures and posters of circus performers. Then you step into the portal, and that's when you fall into the rabbit hole: you're in the world, and all the pre-show performance is happening around you. We wanted it to feel like a space where these circus families are taking over the building, with their living quarters spilling around the big top."

That meant sourcing hundreds of circus props – including several ornate circus wagons – and creating many more from scratch. So how exactly do you go about buying a traditional circus wagon? "Ebay," laughs Law. "That's the first point for everything. And then that leads you to other people in the wagon-selling business. There was a lady from the Traveller community who sold us one of the wagons, and when she arrived to drop it off she had a lizard on her shoulder."

Meanwhile, circus choreographer Tilde Björfors was pulling together a crack team of artists. "It was intense. Circus performers are often booked a long time in advance, so it involved a lot of charming and persuading. Although the performers are presented as families in the show, not many of them knew each other beforehand, so they all had very different opinions and traditions. But when you see them now they look like a family."

A huge part of that is down to the dozens of detailed costumes, which span styles from Victorian to present day, designed by Susan Kulkarni who has worked as one of the main designers for Secret Cinema since its inception.

"We started with 10,000 crystals," she says, "but now we're up to about 30,000. Every single look is bespoke for the show. It's really important that the level of detail is there, because with immersive theatre you get the sense of spectacle while also being in close proximity. People are going to see the details."

Kulkarni worked flat-out with a team of between 12 and 25 people at any one time, matching Hammerstein's creative vision with the practical necessities for each performer. "You can't design anything without knowing what their disciplines are," she explains. In a scene which Kulkarni calls 'the fire section' – yes, it's as exciting as it sounds – she had to make "a bespoke set of costumes at the last minute, because it needed to work in two ways: firstly it needed to worked in the arc of the story. But the costumes also need to be safe, so that we don't set fire to the performers unintentionally."

And as for those songs – A Million Dreams, Come Alive, Rewrite The Stars – the responsibility fell to musical producer Matthew Brind, whose job was to balance familiarity with reinvention. "The songs are a gift. Whatever you do to them, whatever style you throw at them, they stand up, so for example with From Now On we add this Amazonian jungle drum beat which sounds incredible."

Surely, after listening to those songs so many times, he must be tired of them? "I really don't get bored of them," he says. "My relationship with them is better than ever. Sometimes in art, things just come together in this state of real perfection. It's happened a couple of times in opera, it happened with West Side Story, and with Hamilton. And I think it happened in The Greatest Showman. Something happened in that combination of melody and lyrics that will forever be completely magic."

Hammerstein is banking on it. With no script to work from – "I was really reticent to put anything on paper because we were working it out in the room and I didn't want to commit to anything until the last second" – and a rehearsal room that was too small to fit the whole show, it was only during the tech run in the venue that he could finally see it working. "The biggest challenge was having everyone trust me," he says.

Björfors agrees. "We had to get into Simon's head, and maybe try and surprise him a bit. But I think that's what our performers have done. They do intense training every day, they are so dedicated to their discipline and their art. That's what I love about circus. These artists show that we as human beings are capable of so much more than we think we can do. To share that with an audience is to say we can all do more. We can all be better."