Dolly Parton's response to first hearing Whitney Houston's I Will Always Love You

Dolly Parton topped the charts not once, but twice with her heartbreakingly beautiful song, I Will Always Love You.

The 9 to 5 singer originally wrote the track in 1973 for her mentor, Porter Wagoner, after quitting as assistant on his show to go solo.

He thought she was making a mistake and a series of rows ensued, prompting her to pen the emotional song overnight. When she sang it to him the next morning, he burst into tears.

"It's common knowledge we loved and hated each other," she once told Times Free Press. "I was with Porter seven years and promised to stay for five. He was a hard-nosed businessman. I had my own dreams. I stood up for myself. We fought quite a bit.

"When we first broke up, it was hard for him and me. I wrote the song 'I Will Always Love You' for him because he wouldn't listen to what I was trying to say."

For decades the song remained one of Dolly's most beloved, but when Whitney Houston covered it for 1992 blockbuster movie The Bodyguard, it took it to a whole new level.

But Dolly didn't see it coming and reveals in her new book Songteller: My Life in Lyrics how she had no idea the song was even being remade.

She'd had a call from actor Kevin Costner's office asking for a copy of the song, which she duly sent over, thinking nothing of it.

Then one day she was driving her Cadillac home from her office when she heard a haunting intro that struck a chord.

"I had the radio on, and all of a sudden I heard this spoken voice say, 'If I should stay...'" she writes.

"It caught my ear, but I didn't recognise it. Then when it went into the music, I thought I was going to wreck the car. I have never had such an overwhelming feeling.

"I had to pull off to the side of the road, because it just got bigger and bigger and better and better. I have never experienced a greater feeling in my life than hearing Whitney Houston sing that song for the first time.

"I had already taken it twice to No. 1 by then. But she took a little simple heart-broken song of mine and took it worldwide.

"For what she did with that, I will always love you, Whitney Houston. Now the song is going to live forever. "

Back in the day rumours circulated that the song caused a feud between the two iconic stars - something Dolly has said couldn't be further from the truth.

"There was a tabloid story saying that Whitney and I were in a big feud, she said it was her song and I said it was mine," Dolly told CNN in 2003.

However, Dolly insisted there was no bad blood and paid tribute to Whitney's talent.

"I was so flattered, so honored and so lucky that she did it, because the song didn't sound like that when I had it," she said.

The pair went on to become friends and Dolly was devastated when Whitney suffered a heart attack and drowned in a hotel bathtub in 2012 after years of cocaine abuse.

And hearing the song playing at Whitney's televised funeral was almost too much for Dolly to bear.

“[It] just shattered me to hear that song played under those conditions,” Dolly told ABC’s Nightline.

“I thought my heart was gonna stop. It just pierced me like a knife. I can’t explain that feeling, to think that that was so final for her, and that that was my words and my feeling - I would forever be so connected to her.”

For Whitney's part, she always refused to take credit for the hit, insisting that it was Dolly's writing that made it what it was.

She told Rolling Stone in 1993: "I think Dolly Parton is a hell of a writer and a hell of a singer. I was so concerned when I sang her song how she’d feel about it, in terms of the arrangement, my licks, my flavour. When she said she was floored, that meant so much to me."