Barnum: the hardest part in theatre? Just from looking at Fitzgerald, a small (5" 5") but powerfully built man, he's barely joking when he says: "I'm made of brick now." The tightrope scene requires the use of "a million small muscles inside your body. You start walking and you pour sweat instantly. And had he ever tightrope-walked before? Are you kidding me? Why would anybody do that? It's not something I'd ever dreamed of doing. It's a tiny little rope. You can't get off, pull over or take a little break. And I have to sing on it! Fitzgerald and the cast had six days of intensive training to learn a range of circus skills. "They all learned to stilt walk and to juggle, they all did aerial work and they all did whip-cracking," says co-director and choreographer, Liam Steel. The choice and style of circus disciplines used in the final production was influenced by an initial assessment of cast members" differing abilities. "We also had to look for people who had the right attitude," says Vicki Amedume, the show's circus consultant. They've had to do a lot of fitness training on their own, following a programme I've given them. And circus work requires a specific kind of fitness. "It needs a lot of core strength and a lot of shoulder work in terms of the ligaments and tendons you're using," Steel says. It's important that you have the stamina to get through eight shows a week. But Fitzgerald, bubbling over with enthusiasm, loves all of this. "When I was five my Mum put me into clown class," he reveals. She didn't know what else to do with this crazy kid who needed to climb trees, balance chairs on his chin - do all these crazy things. I've always had an affinity for circus stuff, for vaudeville. Physical fearlessness and an acrobatic aptitude aren't the only reasons that the effortlessly engaging Fitzgerald got the job. As well as a great singing voice, "Barnum has to be charming," says Steel. We saw a lot of actors and Chris had that twinkle, that little spark you need in that character. Fitzgerald, 40, grew up in Maine. He progressed from vaudeville in his home state to off-Broadway roles, before picking up a Drama Desk nomination for his performance in Sondheim's Saturday Night. He hit the big time playing Boq in the 2003 Broadway premiere of Wicked and was nominated for a slew of awards, including a Tony, for his turn as Igor in Mel Brooks" 2007 musical Young Frankenstein. More recently he's acted alongside Annette Bening, Matt Dillon and Glee's Darren Criss in 2012 feature film Girl Most Likely. But West Sussex is a long way from Broadway and Hollywood. How did Fitzgerald hear about Barnum in the first place? As well as having previously auditioned for Sheader for a production of Sondheim's Into the Woods, he'd met Mark Bramble in New York and "Cameron knows people that I know. He'd had conversations about who this crazy little guy was," he says with a smile. Steel says that Mackintosh had been keen to do something new with the musical for several years. This doesn't surprise Fitzgerald, who sees an affinity between Barnum's "belief in the essential value of wonder" and the heavyweight producer's "love of the live moment of theatre. It's like he gets giddy when he talks about it. It's inspiring. While this production promises dazzling aerial work and acrobatics - including a stunning duet sequence on the flying trapeze - Steel stresses that audiences shouldn't expect a traditional big-top experience until the Barnum & Bailey extravaganza rolls in at the end. "For the most part, it's about using circus to tell the story emotionally," he says. So, if at any point people applaud a trick that we've done, we'll have got it wrong. Circus elements are woven into the show as our way into Barnum's head, representing his relationship with his wife, Chairy, as well as his limitless ingenuity and imagination. In one scene, Steel reveals, a train station waiting room is built up from people balancing on planks. "It takes things to another level," he says. We're seeing the world as he does. Everything is a lie. This metaphorical, almost poetic use of circus tropes to express Barnum's colourful personality belongs to this production's novel take on the original musical. The team has consciously shifted away from the West End version's "one-man band" element, which, Steel says, "was kind of made around Michael Crawford's skills. Every scene was him doing another trick. Here, while Fitzgerald's Barnum is pivotal, "the ensemble is telling the story with him. We had this phrase at the beginning - they're the riggers of his imagination. The award-winning Steel has worked with progressive performance groups Frantic Assembly, Complicité and DV8 Physical Theatre, as well as Cirque du Soleil. With Barnum, he hopes to meld choreography and circus skills into "something new and original that audiences haven't seen before in mainstream musical theatre." And how does Fitzgerald feel, limbering up for opening night? "It's been a really liberating experience to come into this world where I don't really know anyone," he says. "And it's an exciting prospect, a scary prospect, to walk out in front of people in Chichester and say, "I'm PT Barnum." They're either going to buy it or say, "Where's Michael Crawford?"" Barnum is at the Theatre in the Park, Chichester Festival Theatre's temporary home, from July 15. www.cft.org.uk; 01243 781 312