Poor Elle Macpherson. She gave nine years of devotion and two beautiful children to the fabulously wealthy Arpad Busson, but never persuaded him to marry her.

The simple explanation, we were led to believe, was that his staunch Catholicism precluded marriage to a divorcee such as Elle.

Imagine the supermodel's surprise, then, to read the following entry in the personal columns of The Times last weekend: 'The engagement is announced between Arpad, son of Mr Pascal Busson, of Paris, and Mrs Florence Harcourt-Smith, of South of France, and Uma, daughter of Mr and Mrs Robert A. F. Thurman, of New York.' 

Odd couple: Twice-divorced Uma Thurman is engaged to marry model Elle Macpherson's ex Arpad 'Arki' Busson

To the uneducated eye this could be a fresh-faced couple setting out in life together. To Elle, however, the cheery paragraph will have meant something altogether different.

For Uma Thurman, betrothed to Elle's former partner, is hardly a young innocent. The 38-year-old Hollywood star is the veteran of not one but two failed marriages.

And while Elle converted to Catholicism, such was her devotion to the hedge fund tycoon affectionately known as 'Arki', Uma is an agnostic whose father was the first Westerner to be ordained a Tibetan Buddhist monk.

Small wonder that friends say Elle's perfectly formed nose is out of joint.

'Proposing to Uma of all people makes a mockery of all his old excuses,' a friend told me this week. 'Plus it's not fun for Elle having her nose rubbed in it everywhere she looks.

'Arki could have kept it low key out of respect for Elle and the children, but instead they are going for maximum publicity. It's all a bit tasteless.' 

The happy couple are not hiding their light under a bushel. Their newspaper announcement was followed on Tuesday night by an engagement party of stellar proportions.

A marquee in the garden of Arki's £10million Kensington home played host to an array of stars, including Elton John, Sting, Sir Philip Green, Jemima Khan, Claudia Schiffer and Damien Hirst.

The only thing bigger than Uma's eight-carat diamond engagement ring (set in 20 smaller stones for good measure), guests say, was her Cheshire cat grin.

'They're a quirky couple,' remarked an admirer. 'Uma's been through a hard time in the past few years. Men have let her down in a big way. So to find a genuine, charitable guy like Arki who is so obviously crazy about her is a blessing - and she knows it.' 

Hollywood lovers: Uma and her second husband Ethan Hawke

Uma (who is understood to be keen on a wedding in a British castle) has told her close circle of confidantes that she is ecstatic at Arki's proposal.

She met the 45-year-old financier and philanthropist at a dinner party in Milan last summer, having just split up from her partner of three years, the New York hotelier Andre Balazs. 

The star had also endured three years of being stalked by a psychiatric patient in her native New York, and prior to that the painful collapse of her marriage to fellow actor Ethan Hawke, with whom she has a daughter, Maya, nine, and a son, Levon, six.

Yet despite being happy that Uma has found love again, privately some friends of the star are worried about her relationship with Arki.

'Uma is insecure and it's definitely Arki who has the power in their relationship,' confides a close friend. 'If he snaps his fingers, she comes running.'

Friends say this insecurity stems from the breakdown of her most recent marriage. (She was also married to British actor Gary Oldman in 1990).

Uma said of her 2004 divorce from Hawke that it was 'excruciating' and that her self-esteem had been 'pretty mangled' by the experience.

'All of a sudden she found herself all alone with two children, and at 35 facing up to the fear that in Hollywood terms she was over the hill,' says a friend. 'But Arki is madly in love with her and lavishes her with attention.'

At least in him she has found someone who is as unconventional as she is. Having been raised in India and the U.S. hippy mecca of Woodstock by her model mother (who was married to LSD guru Timothy Leary) and Buddhist monk father, she has always considered herself to be on the fringes of ordinary society.

And Arki, who was educated in France and Switzerland, has never been conventional, either. He grew up surrounded by wealth and privilege before making his £200million fortune. 

Supermodel ex: Arpad Busson has two children with Elle Macpherson

A number of stories circulate about him, such as that he made his first profit selling toothpicks, masqueraded as an Italian prince and that he dated former Charlie's Angel Farrah Fawcett. He denies the first two rumours, but admits to dating Fawcett.

'To be honest, he probably did tell people around here that he was Italian royalty because that would suit his quirky sense of humour,' says an acquaintance of Arki's in St Tropez.

Arki's relationship with Uma, who found fame in films Dangerous Liaisons and Pulp Fiction, follows nine years with the Australian model Elle Macpherson, with whom he has two sons, Flynn, ten, and Cy, five.

'Arki would be bored with a nobody on his arm,' says one of his social set. 'He's the sort of guy who only dates models or actresses.

'He fell in love with Uma when she played Mia in Pulp Fiction. He said one day he'd make her his wife. With most people you'd say it's just talk, but you never underestimate Arki - he can achieve the most incredible things.

'Arki was saying after they first met that she's as intelligent as she is beautiful and if they had to spend a hundred years together they wouldn't run out of things to say.'

And a friend of Uma's agrees: 'She thinks she's finally found her soul mate. And although he has this reputation as a jet-set playboy, he does some amazing things for charity, which he keeps quiet.

'Uma is used to Hollywood celebrities such as Angelina Jolie and Brad Pitt donating money to charity and then telling everyone about it, but Arpad does it more seriously.

'These days his life is organised with military precision by his PA, Steph. Time is split between running his business, fund-raising for his charity ARK and managing his personal life.'

Philanthropy, friends say, is of paramount importance to Arki, and he was thrilled when Uma auctioned off a speaking part in her next film, Eloise. It raised £480,000 for ARK.

Nevertheless, the couple have had to overcome the difficulties of living on opposite sides of the Atlantic.

After they are married, however, friends say they are planning to set up their family in a big country pile in the English countryside.

'She says that she wants a place where she can bake cakes and live like Mary Poppins,' says a friend. 'She's half-joking, but deep down nothing would make her happier.'

The towering Elle, meanwhile, has been spotted out and about with something looking suspiciously like an engagement ring on her finger, despite being ostensibly single.

Since separating from Arki three years ago she has been linked with a number of men, including John Hitchcox, a property developer, and most recently 21-year-old Vito Schnabel, the son of the film director Julian.

Her spokesman, however, stated there is 'no news to report at this time'.

No doubt she would prefer it if the same could be said of the father of her children.