The diminutive pop star, who had a global hit with song Shout, revealed she avoids putting any strain on her voice by banning herself from speaking before midday when she’s on tour.

As well as piping down, the 68-year-old, who practises yoga, is also mindful of what she eats and drinks to keep her vocal chords in tip top condition.

"If I’m on tour I don’t talk until after 12, so from 12 to 12 I don’t speak, not if I want to be able to sing every night," she told The Daily Mirror. “You have to take care of yourself – it’s a job – and if you want to do your job, you have to be fit for it."

The veteran Scottish-born singer, born Marie MCDonald MCLaughlin Lawrie, is renowned for her powerful voice and has enjoyed a long career since winning the Eurovision Song Contest in 1969, recently performing to packed houses across the U.K. and Australia. When asked if she has thought about retiring, she was quick to answer, “I’m going to keep going until I can’t do it any more. It’s like a love affair. I love what I do."

The To Sir With Love singer is a guest judge on BBC1 talent show Let It Shine alongside Take That star Gary Barlow. The pair previously worked together on the band’s 1993 hit Relight My Fire.

“Don’t take yourself too seriously," she advised when asked if she had any tips for the contestants. “That is one of the things Take That are known for. They have a lot of humility.”