Supermodel Elizabeth Hurley finally decided to wed longtime beau Hugh Grant --after her widowed mother convinced her that marriage is the key to happiness.

Besides that, the luscious Estee Lauder model -- who many believe is the most beautiful woman in the world -- is insecure about her looks. . . and afraid she'll turn into a wrinkled wreck.

So the 34-year-old stunner, whose biological clock is ticking louder than a time bomb, will marry Hugh this summer -- and get busy making babies!

"Liz used to say that she'd never marry Hugh after he was caught with hooker Divine Brown on Sunset Boulevard," said a source close to the golden couple.

"But her world turned upside down when her beloved dad Roy died in November 1996.

"All her life, Liz watched her parents share their lives.

"When her dad passed away, Liz was left to comfort her mother.

"Liz sees the pain in her mother's eyes. It's made her realize that being alone isn't all it's cracked up to be.

"Liz' mother told her that until you completely give yourself to another human being, you'll never experience true love.

"Her mother also confessed that it's a lonely world without a husband by your side."

With those words ringing in her ears, supersexy Liz has taken a second look at her relationship with Hugh.

"Liz met Hugh in 1987 on the set of a movie. Since then, they've had their ups and downs," said the source.

"But somehow they've managed to build a solid, if sometimes tempestuous, relationship.

"Early in their romance, Elizabeth was dead set against getting married or having kids.

"In fact, whenever her mom, her sister Kate or her friends would ask when she was going to start having babies,

Liz would tell them to mind their own business.

"But things have changed dramatically. Liz will turn 35 in June and she hears the proverbial biological clock ticking.

"She's realizing that Hugh, on the whole, has been very good for her.

"The two of them have built not only a personal life, they're also co-owners of their own production company Simian Films.

"So far they've produced 'Extreme Measures' and 'Mickey Blue Eyes' -- both of which Hugh starred in and Liz produced.

"And everyone who knows Hugh swears he would make the best father.

"He'd love to have four children and live in a mansion out in the English countryside.

"And Liz does want children. In fact, she's gone on record as saying that she thinks mixing her genes with Hugh's would create lovely babies.

"Liz told a reporter, 'If you can envisage your genes mixing in with their genes then that, to me, is the real test.

" 'And I wouldn't mind my genes mixing in with Hugh's. I haven't met anyone else I wanted to procreate with.' "

What's more, Liz is obsessed with losing her cover girl looks.

"She'll stand in front of a mirror in nothing more than bra and panties and moan about how she's aging," said the source.

"Then she'll call Hugh over and have him examine a new wrinkle on her face.

"Hugh goes along with her. He'll say, 'It's true, old girl. You're falling apart!'

"It drives Liz crazy, but she's thankful that Hugh can laugh and joke about her insecurities.

"She knows Mother Nature takes her toll on the rich and beautiful as well as the average person -- and she's no exception.

"She just needs to get that ring on her finger and settle down.

"Otherwise, she'll wind up all alone -- bitter, jealous and aging."

-- SUZANNE ELY - National Enquirer