With its feelgood story of a child dance prodigy who fulfils his dream in the face of seemingly insurmountable odds, Billy Elliot: The Musical has earned a lasting place in the hearts of the British theatre-going public.

But while pure natural talent, tons of enthusiasm and some encouragement from a local teacher might be enough to get Billy into ballet school, in today's competitive arts world, being a successful dancer typically takes a lot more in the way of hard work, intensive training and unwavering family support. Unlike the character, the boys who play the part undergo months of classes and rehearsals in a specialised school before they ever find themselves on stage.

Following a sneaky look behind the scenes of the UK touring production in its current home at Birmingham Hippodrome, we caught up with some of the cast and crew to find out more about what it takes to make a Billy.

“All of the boys go to what's called 'Billy School' for a couple of years until the team thinks they're ready to start training for the shows,” explains Assistant Company Manager Emma Nicholas. “That's just to get them to the point where they're fit enough and technically skilled enough though – then the actual training for the show is another six months. So when our current boys started this tour last year, they'd already been preparing for two or three years.”

But even this is only part of the process. Before they even enter Billy School, the would-be stage stars have already been through two auditions and a summer school.

“If the boys pass a base level of technique [in their first audition], we send them back to their own schools with feedback, and then we bring them back again for another test,” says Resident Choreographer Jeroen Luiten. “If they have made the necessary improvements, they then go into the summer school where for 2-3 weeks we very intensely train them in aspects of the show. If they then pass another audition after those three weeks, that's when they're sent to Billy School.”

Ability isn't the only thing they're being tested for – what is arguably even more important is their absolute commitment to the job and to being the best Billys that they can possibly be.

“You can only do this if it's absolutely what you want,” Luiten continues. “There's a lot that you can teach in terms of technique, but if they are not 100% driven, they will not get through our rehearsal process, and you can tell pretty fast if they're not.”

The strict schedule means that its not just the boys who must be completely dedicated. Towards the end of the show, when Billy finally gets to his audition for the Royal Ballet School, the panel interviewing him is keen to stress to his rather bemused father the importance of wholehearted family backing for Billy's choice. This is something that rings absolutely true in real life, too.

“It's a really big commitment for families,” says Luiten. “Mum and dad need to be willing to bring them out to us, and for them to be staying with us for three weeks at a time before they go home for a week, and then come back again.”

If you've yet to see the show first hand, rest assured that the long months of training all pay off: the Billy boys are some of the most adept, confident and natural-seeming child performers you're ever likely to see on stage. As well as mastering acting, singing and Geordie accents, they're also expected to be proficient in a mix of ballet, tap and acrobatic styles. Yet there's still plenty of room for each one to make the part their own, and subtle differences in the skills, talents and personalities of each performer means the show is well worth seeing more than once, if you can make it.

“Each version of the 'Electricity' routine is based around the individual boy, so none of them are the same,” Luiten says. “The dance supervisor, Ellen Kane, looks at each one to see if they're a right turner or a left turner, a right jumper or a left jumper, and recreates the choreography for them. The main development in the routine generally is that nowadays there is way more of an acrobatic element than there was at the start, since all of our boys currently are very strong on acro.”

Crucially though, the dance should always be expressive of story and character – never simply a case of showing off technical skills just for the sake of it.

“Peter Darling [the original choreographer] works from an acting point of view, so all of his material is story-related, and all of his moves mean something,” he continues. “I'm mainly here to maintain Peter's work, so I would never take credit for something I didn't create, but one of the things I can do is adapt the difficulty of routines if I feel that one of the boys is ready for a new challenge. In that instance, I'll email Peter to make sure that he agrees to any changes – I do nothing without his approval.”

Along with 'Electricity' – the big finale when Billy wows his interviewers and audience by demonstrating what he's capable of – the other major routine that is carefully set and diligently rehearsed is 'Expressing Yourself' – a tap duet with Billy's best friend Michael. To ensure that the percussive sound of the tap dancing can be heard over the sound of the orchestra and singing, the three actors playing Billy, Michael and dance teacher Mrs Wilkinson all have two extra microphones hidden in the clothes around their legs.

“There have been boys in the summer school who have auditioned for Billy but ended up playing Michael instead. Vice versa it's more complicated though, since Michaels are only tested on tap,” says Luiten.

Interestingly, it's not just the complex, intricate routines that can be tricky. One of the hardest jobs for Luiten is teaching technically outstanding children how to dance badly earlier on in the story.

“It's very challenging trying to make someone who is really professional material look like he's only just learnt it, particularly in sections like 'Solidarity',” he admits.

But while training to be Billy is a long and demanding process for such young performers, at least it's not an experience any of them go through alone. New Billys are introduced in groups of four, allowing them to share the role and ensuring that everyone gets enough time off to rest up and come back refreshed and ready for the next three weeks. On any given night, one of them will be on stage, one will be on standby at the theatre, one will be nearby in a hotel, and the fourth will be spending a week at home with his family.

“We keep the same ones for the duration of the tour, but in London, they'll be with the company for about a year – maybe a bit longer. It all depends on how they grow,” says Nicholas.

“Already you can see that ours have really shot up,” adds Scott Garnham, who plays Billy's older brother Tony.

“It's been a year now since the opening, and just in themselves they've really matured as well, which is lovely to see,” Nicholas agrees.

For schoolboys, the three or four years that the training and performances take up together accounts for a huge chunk of their lives. In consequence, their inevitable departure from the show is a massively big deal for them, something akin to moving home, changing schools and having to start their lives afresh elsewhere. Happily, special provision is made to help them move on and readjust to life outside the world of Billy Elliot.

“It's such a big thing to do, especially at that age, so even when they finish there's a whole rehabilitation process where they help the boys to get into drama schools or whatever – they don't just drop them!” says Garnham.

It's a rather different situation to the one in Luiten's native Holland, where the children were only permitted to appear in a total of 24 shows per year! And that's not the only major difference for productions of the show overseas as opposed to those in Britain.

“I think it's a really English story. We never had a mining community, and of course we didn't grow up with the whole Maggie Thatcher thing,” he says. “The people who came to see the show in Holland absolutely loved it, but the audiences here are way more committed to the story, because it's about your history.”

Billy Elliot is at Birmingham Hippodrome until Saturday 29 April. Tickets are available from birminghamhippodrome.com.