The collapse of their relationship surprised many industry observers, who viewed the marriage as one of the strongest in Hollywood.

Cruise described his first meeting with Kidman, on the set of Days of Thunder in 1990, as "sheer lust".

He left his first wife Mimi Rogers and the couple married the same year, rapidly becoming Hollywood royalty.

The couple adopted two children Isabella and Connor, now 13 and 11 respectively, and juggled their work schedules to ensure a stable home environment.

Publicly and professionally they appeared united and content.

In 1998, the couple won substantial damages at the High Court in London after the Sunday Express claimed their marriage was a sham.

The actress herself called their 2001 divorce "a major shock".

"To me, he was just Tom," Kidman told US magazine Ladies' Home Journal last month. "He was lovely to me. And I loved him. I still love him."

According to divorce court file papers, Kidman begged Cruise not to end their marriage and later miscarried a baby she was carrying.

Within months, Cruise was dating Vanilla Sky co-star Penelope Cruz.

Nonetheless, personal distress coincided with professional triumph for Kidman. A string of critically acclaimed roles thrust her into the awards spotlight and saw her win an Oscar for playing author Virginia Woolf in The Hours in 2003.

The actress also had a hit single in the UK, duetting with Robbie Williams on the Nancy Sinatra cover Somethin' Stupid which took the coveted Christmas number one spot.

As one of Hollywood's highest paid stars - and newly single - Kidman's love life became the focus of tabloid speculation.

Close friend and fellow actor Russell Crowe and singer Lenny Kravitz were both rumoured to be dating the actress.

In 2003, the actress won undisclosed damages from two British newspapers who wrongly claimed she was having an affair with married Cold Mountain co-star Jude Law.

There were also suggestions that Kidman and Cruise might get back together.

"We have very different lives now but, as I've said to Tom, I will be there for him for the rest of his life, always there," the actress told People magazine in 2003.

For his part, Cruise told the Daily Telegraph in December that year: "I have always loved Nic and I always will."

But last June, Cruise announced his engagement to Katie Holmes. Their whirlwind romance dominated headlines, with Cruise describing Holmes as "just amazing".

Kidman, whose meteoric career had recently stalled following a number of high-profile flops, said of her ex-husband's new romance: "I hope he's happy."

She herself was rumoured to be dating New Zealand-born singer Urban, 38, whom she met at an awards dinner in Los Angeles in January 2005.

Unlike Cruise and Holmes, the pair, who were both brought up in Australia, conducted a low-key courtship away from the media spotlight.

In May this year, they confirmed their engagement after Kidman was spotted wearing what appeared to be an engagement ring.

"He's actually my fiance," she told People magazine. Urban's publicist, Paul Freundlich, later confirmed the couple were "happily engaged".

A homegrown prodigy, Urban moved to Nashville and won the Grammy award for best male country vocal performance last year - but only after he beat addiction to cocaine in the late 1990s.

As she celebrates her 39th birthday on Tuesday, Kidman could be looking forward to a life of domestic bliss with Urban in Nashville.

"I think probably when I fall in love, that's when I will stop doing as much as this because I will want to settle down again," she said in Cannes in 2003.