shocked fans by revealing the true meaning of his song, Someone You Loved.
The 23-year-old superstar achieved global success with the melancholy hit which stormed the charts for weeks.
The singer's ex-girlfriend, Paige Turley, who stars in the current series of Love Island, thinks the ballad is about her.
In an interview before the ITV series first aired Paige apologised to Lewis, 23, under the impression his heartfelt lyrics told the story of their doomed relationship, which ended a couple of years ago.
The 22-year-old blond beauty from West Lothian said: "According to the papers they think the song was about me.
"The song was called, Someone You Loved.
"If that's the case, Lewis, I'm so sorry."
She added: "My expectations are high.
"If I've got a song written about me, boy, you better be bringing it."
But Lewis shot down those claims with Australian music channel, VMusic.
Lewis, also from West Lothian, revealed that the song doesn't pay tribute to Paige, but his late grandmother.
He said: " The song is not about a lady who I was in a romantic relationship with.
"It's about my grandmother, who's dead.
"She died a few years ago.
"Your classic death, you know what I mean?
"Not coming back sort of thing."
Lewis also admitted that his most successful hit to date almost didn't make his first album, Divinely Uninspired To A Hellish Extent.
"I was writing for the album and I thought the album was finished," he added.
"And I had this little thing in my head, 'you could try just doing one more' and I did try and do one more for three months and nothing was coming.
"And then one day I was sat at my piano, after the death, and I sat down and I started messing around.
"That's why the piano part is so simple, because I can't play anything else.
"Bing-bing, bing-bing, that's it.
"I got all the melodies down but I couldn't think of any lyrics.
"So I was like, 'oh well, I'll just wait till the second album' and I'd put it on the second album.
"Thank f**k I never did that, because my career would have been an absolute f*****g tail spin, I would have flopped hard."
The singer then opened up about how the touching nod to his late gran made the record in the end.
Jokingly, Lewis said: "Then I went into a session with friends of mine called TMS and a guy called Romans.
"I was like, 'I've got this but I can't write another heartbreak ballad'.
"As fortune had it, my gran had just died.
"They said, 'have you lost anybody?' and I said, 'just the ticket, my gran's dead'. "
