The English actress trained for months to get herself in shape for the role

When Esme Creed-Miles landed the lead role on Amazon’s new series Hanna, she knew her life was about to change.

“I was with my mum and we were walking down the stairs of our apartment building when I got a call from my agent,” she tells PEOPLE in this week’s issue of learning she got the part. “I nearly fell down the stairs.”

Naturally, she immediately went out to celebrate.

“My friend and I went to dinner and I ordered the lobster pasta, which was the most expensive thing on the menu,” she says. “Then realized that my card was probably going to be declined because I only had my student allowance.”

Credit: Jamie McCarthy/Getty

Based on the 2011 action movie starring Saoirse Ronan, Hanna follows an isolated teen (Creed-Miles) raised in the forest by her ex-government operative father. Together, they try to evade the pursuit of an off-book CIA agent.

Creed-Miles, the daughter of actors Samantha Morton (The Walking Dead) and Charlie Creed-Miles, trained for months to get in shape for the role.

Esme Creed-Miles HannaCredit: Jonathan Prime/Amazon
| Credit: Jonathan Prime/Amazon

“I was shocked at how hard some of that stuff was and I really needed to focus. I really needed to not be as lazy as I tend to be most of the time,” she says. “I really needed to train hard, for a good few months, before the show started. I had to learn martial arts.”

And while she was resistant to the constant exercise at first, the actress says it eventually became an escape from the stress of filming.

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Credit: Perry Hagopian

“It became something that kept me sane,” she says. “Sometimes punching a bag for half an hour was pretty cathartic and pretty necessary.”

Also starring Joel Kinnaman, Hanna launches March 29 on Amazon.