Samantha Womack added vodka to her water to "keep things fresh" on stage during The Girl On The Train.
The 46-year-old actress - who is most famous for playing Ronnie Mitchell in EastEnders until leaving the long-running soap in 2017 - has opened up about her role as alcoholic anti-hero Rachel.
Rachel believes she witnesses a crime from the window of her train, and Samantha admitted she likes to "try all sorts" of techniques to keep the production enjoyable rather than "boring".
However, Samantha's decision to drink on stage may not have been her best idea.
She said: "I try all sorts of things, when you're doing a long play, we've extended this tour twice we're in West End until Saturday and then the tour continues until November.
"There was one time I put vodka in the water and I felt slightly unhinged and a bit looser.
I put vodka in the water but I felt slightly unhinged.
"All of those things things I really enjoy, it keeps things fresh for me, so it's not boring... for them."
The Kingsman: The Secret Service star only has a 10-minute break in the production but doesn't find it too taxing.
Appearing on ITV's Lorraine on Friday (August 16), Samantha added: "There's just a pee break halfway through because I'm necking vodka, not actually vodka, it's water, yeah, like a 10-minute break and just back on.
"The momentum and energy keeps you going."
Samantha - who has Benjamin, 18 and Lily, 14, with her husband Mark Womack - is often joined by her daughter backstage, and the star revealed she provides a "grounding" influence
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She continued: "I've got Lily, I home school her, she's 14 and she's in the dressing room most of the time.
"You know the truth of it is, I'll come off stage in the midst of a performance and she'll be saying do you want this vegan salad and I'm in the middle of the play!
"It's very grounding, very helpful."
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