‘I was like what the f**k?’ says Lucy Spraggan as she reveals surprise way she learned of collaboration with pop star

X FACTOR legend Lucy Spraggan has revealed the surprise moment an iconic pop star told her they were working together.

This Friday a new version of songwriter Lucy's much-loved track Sober will be released to the world featuring a very familiar voice.

None other than Robbie Williams, 50, lent vocals to the song, which is about Lucy's past struggles with alcohol and her determination to give it up.

In an exclusive interview with the Sun, she revealed how X Factor supremo Simon Cowell pulled strings behind the scenes without her knowing to secure Robbie's services.

Lucy, 34, explained: "Simon's been going through the back catalogue and trying to work out what songs we're going to use in the future for this reworked album. And he got a hold of Sober and he's like, 'I love this song. Do you know who should hear this song?'

"He was like, 'Robbie has to hear this song'. I was like, 'oh my God, I'm supporting Robbie in July'. He's like, 'no'.

"And then I met Robbie at Sandringham and we had a chat for like 25 minutes in the dressing room and then I was like, 'have you heard the song Sober?' And he was like, 'yeah, we're working together on it, aren't we?' And I was like, 'what the f**k?"

Pop legend Robbie is woven into the fabric of British music thanks to his 90s and noughties hits, from his early career with Take That to his wildly successful solo material.

His star is still soaring having recently sold out his headline show at Hyde Park's British Summertime event.

For all his fame, Robbie's kept his feet firmly on the ground and Lucy said he's shown her nothing but kindness.

"He actually sent me a text yesterday and he was like, 'can I call you?'" she said. "And he called me and just Facetimed me for like a bit and said, 'if you need anything, if you have any questions, like if you need any support or anything, I'm here for you'. And I really appreciate that.

"Like people, any walk of life, no one has to be that kind. And so I really just have a lot of respect for him."

Robbie was also amazed by Lucy's dramatic body transformation after she changed her lifestyle and became dedicated to fitness.

She said: "I remember him being like, 'how did you lose all the weight?' And I was like, 'sobriety, dude. Like I literally got obsessed with running and I wanted to have a fight at some point'.

"And he was like, 'you have to do that at some point'. Now I'm like, I'm going to have to have a professional fight because Robbie Williams told me to."

Sober documents Lucy's previous reliance on alcohol and her decision to move away from the guilt and shame she felt when drinking.

The person she is today no longer needs alcohol to make her feel comfortable and she describes her sobriety as a "superpower".

She said: "The thing that most people don't realise is that a lot of us use alcohol to cope with things. So when you remove that, you need to find other things.

"You need to be able to be in touch with yourself enough to know that, oh, like, 'I'm really stressed'. So I need to manage that stress. So I never think to myself, 'oh, maybe I'll just go and have one drink' because I'm confident enough now I dance at weddings completely sober, like that's hardcore sobriety stuff there.

"But I don't need anything to fall back on. I've got myself.

"I think a lot of people are taught that sobriety is this horrible, laborious, stressful, sad and lonely experience. But sobriety has been, I've been so supported. And I think it's my superpower and I have zero shame about my drinking days or anything like that."

Indeed, the sky really is the limit now, and Lucy is riding a purple patch.

She became the first X Factor star to perform at Glastonbury last year, was invited on tour by James Blunt, has her own headline run coming up and another album release scheduled for early next year.

What does she make of it all?

"I'd have given myself a glass ceiling because I would never have anticipated there would be any reality where I could do a duet with Robbie Williams.

"So instead of setting these goals that I might well achieve, I'm just keeping an absolutely open mind to the fact that like anything is possible and to just really embrace everything as it comes."