Ruthie Henshall always thought she was far too “airy fairy” to write a book. But the one she has just produced on working in musical theatre, with a little help from her journalist dad, the musical director Daniel Bowling, gives a comprehensive and cogent insight into the world she knows inside out.

The book intersperses cautionary tales from her illustrious career, from Miss Saigon to Marguerite, with invaluable advice on training, auditioning and how to conduct yourself in rehearsals once you’ve landed the job. After more than 25 years’ experience in musical theatre on both sides of the Atlantic, Henshall very evidently knows what she is talking about.

“It takes hard graft to succeed in musical theatre,” she says. “I trained for nearly ten years, so when the time came for me to grab the limelight I was ready. Consistent, dedicated work is the only way.”

Henshall does not pull her punches about how tough it can be for anyone trying to make their mark in musical theatre. Your body will endure every imaginable punishment over time, she says, and your strength of character will also be tested to the limit.

Delivering eight shows a week requires enormous reserves of stamina and focus, especially when it comes to your voice. Exercising your vocal chords daily and living a healthy lifestyle, with a balanced diet and plenty of sleep, are absolute essentials for anyone hoping to make it as a musical performer, she says.

How to prepare for an audition takes up a whole section of the book, from choosing songs and what to wear to how to behave on the day. Henshall writes that every audition teaches you something, whatever its outcome. “If you worked hard, did your best and come out empty-handed, you just have to shrug your shoulders and hope for better luck next time. If you’ve got what it takes, you will be found.”

If the leading person is a shit it filters through the whole company

Even though she was already playing leading roles in her early 20s, Henshall considers herself a late starter. “I didn’t actually realise that’s what I wanted to do until I was ten years old,” she says, apparently serious. In her final year of primary school, having been a tomboy for years, she saw another girl practising ballet in the playground and found it mesmerising. “My world suddenly came into sharp focus, like somebody turning a light on. I wanted to be a ballerina right up to the time I had to choose a college,” she says. “But I wasn’t disciplined enough, I was the wrong shape and I wanted to do everything – dance, sing, act.”

So her secondary school dance teacher suggested Laine Theatre Arts College where she could hone her music theatre skills. “I started out doing the dancers’ course, then I swapped to music theatre as soon as they introduced the course. I never had any doubt in my mind that I would make it.”

After her first big break, playing Ellen in Miss Saigon, at 21, Henshall simply told herself she wasn’t going back to the chorus. Starring roles in Crazy For You, Oliver! Chicago, The Woman In White and Marguerite, among others, followed.

Julian Ovenden and Ruthie Henshall in Marquerite at the Theatre Royal Haymarket, London. Photo: Tristram Kenton

Pre-eminent among myriad qualities vital for success in musical theatre, she says, is self belief, something that is either innate or acquired through years of honing your skills.

The other essential quality is resilience, the ability to bounce back after rejection again and again and again. There are no short cuts, she says – being unwanted and sometimes unfairly dismissed is something every actor has to learn to live with.

Henshall also emphasises the importance of being open-minded, flexible and generous in a company, especially during rehearsals when tempers can become a little frayed.

“You must keep your head when all about you are losing theirs,” she says. “I can’t bear bad behaviour. We can all get insecure and snappy when we’re nervous. When you’re part of a company you work very closely with people so it is not fair to create a bad atmosphere. If the leading person is a shit it filters through the whole company. I experienced some of that earlier in my career but I rarely come across it now. I feel I have a duty to lead a company and make it fun. If there is a bad egg in the company, I find a way of dealing with them.”

One of the most revealing passages in the book concerns Henshall’s own bad behaviour during the run of Chicago when she received “the dressing down of my life” from the directors Walter Bobbie and Ann Reinking. Here it is in her own words:

“The best directors always strive to create an atmosphere and environment that allows the company to be free and experimental in creating their performances. But on opening night it is the director’s concept of the entire production that will ultimately triumph or fail, so it is essential both artistically and professionally that you listen to and trust their judgment. The director is the ultimate boss; he or she has a vision of how they see the show, and how you fit into it. Of course they will want you to find your own facets and qualities in the role, but never try to take things into your own hands, as I did when I was creating my performance as Roxie Hart in Chicago.

“After weeks of being directed I began to feel Roxie was becoming too much of a caricature. I wanted to strip it back to the sleek lines of Bob Fosse, and stop worrying about putting too much extra on top of that. I discussed these reservations with the director, Walter Bobbie, but perhaps didn’t explain myself as well as I might have done; very sensibly he wanted it played as he had directed it on Broadway. Somewhat impetuously I took matters into my own hands and performed the role my own way at the first preview. It sent the whole creative team into meltdown, and I received the dressing down of my life.

“I went back to playing it the way they wanted and the show was a great success. I got the chance to reassess the role and get deeper under Roxie’s skin when I played her in New York and at a special tenth anniversary performance in London. So don’t be afraid to speak up if you feel something does not work, or if you can add something beyond what you’ve been asked to do, but always channel it through the director so that their vision is always taken into respectful consideration. Never be afraid to ask a director for more clarification if you genuinely feel what is being asked of you is inappropriate. Don’t ever allow a director – or anyone else for that matter – to bully you into doing something you believe is wrong.”

So You Want To Be In Musicals? by Ruthie Henshall and Daniel Bowling is published by Nick Hern Books, priced at £9.99. To win a signed copy of the book visit enter The Stage’s exclusive competition.

The Sound of Musicals with Ruthie Henshall, Birmingham Symphony Hall, November 4.

Ruthie Henshall and Elaine Paige in Concert, Central Hall, Westminster, November 27