Simon Cowell pays off family's £80,000 mortgage on Oprah...before enjoying a spin in his $1million supercar

Simon Cowell has paid off a family's £80,000 mortgage after being touched by the plight of their three-year-old daughter, who has a rare form of cancer.

The pop mogul pledged to be a "guardian angel" to little Madelaine Stoen after meeting her parents on Oprah Winfrey's U.S. chat show.

Cowell, who was on the programme to promote his X-Factor starlet Leona Lewis, was close to tears after watching a video interview with Madelaine's parents, Randy and Amy, in which they told of the financial burden of her treatment.

When Miss Winfrey brought on the couple and introduced them to Cowell, he told them: "I know you are having problems with your mortgage. As of this afternoon, your mortgage has been paid off."

Since Madelaine was diagnosed with an aggressive form of cancer last month after developing a cyst in her nose, the Stoens have had to travel more than 100 miles from their Minnesota home each day for treatments.

Madelaine, who is starting to lose her hair, faces a year of being in and out of hospital as she undergoes radiation treatment.

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Simon Cowell showed his caring side by paying off the $162,000 (£80,000) mortgage of a couple whose daughter has been struck down by cancer

Millionaire around town: Simon took his $1million car for a spin, after discovering that it does actually feel good to help others. He credited Oprah for his new-found caring side

Later Cowell told Miss Winfrey: "The money for me is not the important part. It's when you see that film and that little girl.

"I said to the parents, 'It doesn't stop there. If there are any problems, I'm her guardian angel now.'"

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Winners: Simon appeared on top-rated chat show Oprah alongside protege Leona Lewis, who is launching her album in the US