United Kingdom, April 19 -- Christie Brinkley's marriage to Billy Joel was "painful" by the end.

The 71-year-old model tied the knot with 'Uptown Girl' singer Billy, 75, in 1985 and even though there was a time that she felt like the "luckiest girl", the whole relationship just eventually stopped "functioning" so they divorced after almost a decade together..

Writing in her new memoir 'Uptown Girl', she said: "I still believe in love.

"There were a few doozies. I had two great loves, [my first husband] Jean-Francois and Billy. We laughed like you couldn't believe.

"And seeing him in concert.

"I felt like the luckiest girl in the whole arena. I liked to be right in the front row by the piano so he could glance at me and I could look u...