Britain’s Got Talent star Lucy Kay always had an inclination that X Factor boss Simon Cowell had a soft spot for her – especially as he was one of the first to Tweet his congratulations when she landed a multi-album deal with Sony.

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But Lucy, 24, tells Closer that she was blown away when Simon’s girlfriend Lauren Silverman invited her to sing at his 55th birthday party at West London restaurant Scalini recently.

Lucy says: “I had the chance to sing Nessun Dorma, that is one of Simon’s favourite songs and when I had finished my performance he gave me a hug and a kiss on the cheek saying it had made his night. It was very surreal.”

And the appreciation is certainly mutual as Lucy adds: “I said to Simon 'you've changed my life' and he replied 'no, you have changed my mine.' I wanted to reply 'how can I possibly have changed your life? But it was nice to hear those words from him nonetheless."

When it comes to Simon and Lauren, 36 – who is mother to Simon’s eight-month-old son Eric – Lucy reveals they are incredinbly loved-up.

Lucy says: “They are very affectionate towards each other. It was weird to see because you rarely see that side to him. She got quite teary towards the end of her speech when she said ‘seeing you happy is what makes me happy. I love you Simon.’ I felt honoured to be included in that moment.”

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The Britain's Got Talent opera singer has already announced she will tour next year with Collabro – who also performed for Simon at the event.

Lucy's debut album Fantasia is out now