The Tchenguiz sister

'Losing your home, your school, all your friends, your country, your life... it took us a few years to settle down. We always thought our move would be temporary - a year, two years, three years - we still thought we would go back some day. So we didn't put down roots here for a good four years.' They were luckier than most because all of them were out of the country at the time - Vincent and Robert were studying at American universities - and so they were able to survive.

The experience made her parents still more protective of her. 'They still are,' she says fondly. So while her brothers were encouraged to forge ahead, building up their property and finance empire on the back of Victor Tchenguiz's successful London property investments, Lisa studied fashion design at the American College in London.

She clearly has her fair share of the family brains and savvy. 'Vincent had this impression that I was the brightest of the kids,' she admits, 'because I was very studious. So he decided I should go into insurance because he was in finance and Robbie was in property, so we would cover all the bases.'

(Left) Lisa Ray and Sheetal Sheth in 'I Can't Think Straight'

Taken on at the age of 17 by Hambro Life, her first job was to write a list of the richest people she knew, estimate their wealth, then write to them offering them life insurance. 'I didn't sell one policy,' she mourns, which seems hardly surprising. Then her brothers organised another non-job by giving her a desk at their company, Rotch. 'They told me to find myself something to do, so I decided to call myself head of PR,' she laughs. 'That lasted for about a year. Nobody gave me any direction. My dad would come in, pinch my cheek and say, "Oh, you're working today!" Basically, what they all wanted me to do was what was expected of me: to get married and have some children.' So she decided to oblige.

Lisa's own parents, who are both Iraqi Jews by origin, had a semi-arranged marriage. Her father spotted her mother walking beside the canal in Baghdad, and introduced himself to her father at a café. Several coffees later, the deal was done. 'My mother was at home when her mother came in and told her that she was having an engagement party the following week.' The couple 'dated' for five days, heavily chaperoned, then married in Iran.

Fifty-four years later, they are still together and, says Lisa, happily so. The same cannot be said for Lisa, who made her own choices. Her first marriage, when she was 30, was to the perma-tanned DJ Gary Davies, whom she'd met at a wedding in Manchester. 'I didn't really know who he was, or the celebrity status he had,' she says. 'In our first year when we were dating, I did a road trip with him around the UK. It was an amazing experience. I remember 10,000 people coming to one of his concerts.' A further 1,500 went to their wedding, but they had no children and the marriage ended in 2001 when Lisa walked out.

'He's a nice man, very nice,' she says briskly. 'I don't have a bad word to say about him. We just didn't get along towards the end. I don't see a lot of him, but we're still friendly. His sister is one of my good friends.'

Lisa bounced straight out of one marriage into another, hooking up with Vivian Imerman, the South African fruit juice tycoon, and marrying him that same year. Their daughter Ariella was born in 2002.

The glamorous Imermans were a staple of the social scene: their Mayfair townhouse was the scene of endless elegant dinners, and they wafted around town in his 'n' hers Rolls-Royces. Lisa's role was to be the perfect hostess, wife and mother, and her own ventures were confined to a bonkerssounding project: a restaurant in St Tropez with Ivana Trump, which was run by Trump's toyboy husband Rossano Rubicondi. Was it a success? Embarrassed laughter. 'It was an experience. We had a lot of fun.' (Despite the presence of diners such as Joan Collins and Roberto Cavalli, takings can't have been high since almost every evening the place was taken over by one or other of its glamorous patrons for a private party.)

Towards the end of last year, cracks began to appear in the Tchenguiz-Imerman partnership. Lisa doesn't say what split them up, though Imerman's first marriage ended because of his infidelity. 'I haven't done well with my marriages,' she admits with a sigh.

But this time the separation has been a bitter one. Over the past few months the gossip columns have been buzzing with juicy revelations about the divorce battle which promised to be as entertaining as McCartney vs McCartney.

Lisa's ever-protective brother Robert banned Imerman from entering the Mayfair office block the three brothers-in-law shared; Imerman secured an emergency injunction from the High Court to retrieve his possessions. Negotiations over the matrimonial millions have included fights over the ownership of the bulletproof car.

Even the lawyers got fed up. 'I hope that I will never see this case again,' said exasperated High Court Judge Nicholas Warren. 'I will transfer this to the Family Division if it ever comes back before me.'

But Lisa says that the rows have now stopped. 'My husband and I are in an amicable place,' she says. 'It was bitter, yes, but we're both on the same page when it comes to our daughter, and that's opened up an amazing dialogue. We speak because we love Ariella. She's our focal point and we've decided to concentrate on her life. I saw what the divorce was doing to her - it was hurting her a lot - and the anger wasn't helping any of us. I don't want this to affect her in any way. She's a really happy child, she's kind and sensitive, and the last thing either of us wants to do is upset her. So we're keeping it civilised.'

No more rows about money then? 'We're not talking about finances, we're talking about Ariella,' she says instantly, native canniness asserting itself before she bursts into roars of throaty laughter. 'But hopefully no more rows about finances. So that's good news.' For everyone except for the gossip columnists who will have acres more space to fill.

(Right) Vincent Tchenguiz outside his Mayfair office, October 2008

So, for the first time in her life, Lisa Tchenguiz finds herself without a male protector. And at the same time, her parental security blanket has been removed: her mother has been seriously ill with cancer and is still in hospital, and Lisa has found herself in the role of carer. 'Initially, I was quite sad and scared,' she confesses. 'I didn't know what to do with myself. I felt, "Oh my God, I have to cope with everything." Like bills - I'd never had to think about them. But I've realised it's just life, it's what everybody copes with.' Now she seems finally to relish being in control of her own life. 'If I've got builders in, I'll go and bargain with them,' she says. 'I go into my office almost every day to manage my money.'

Tellingly, she has lost much less in the credit crunch than her brothers - Robert is said to be worse off by £1 billion. And she has started to enjoy her single status. 'I can sleep as late as I want, I watch TV in bed, my house is always full of people, which is nice for my daughter. There's a very good energy to it.'

She credits her renaissance to the friendship of Hanan Kattan and Shamim Sharif, and is now considering investing in a third, Russian-themed, film of theirs if the first two make money. And if she has inherited anything of the family Midas touch, they surely will.

'Hanan and Shamim explained to me what I'm capable of doing when I couldn't see it. I was so busy just being a mother, I didn't know what other direction I could take. But Ariella is at school most of the day and I need to find my own life now,' she says.

That's not to say that she wouldn't marry again. In fact, she says she'd like to 'but as an adult in a mature relationship of equals'. She hopes for more children into the bargain. 'But what I really want to do now is learn to enjoy my life and to be single again. I always thought I was independent - I manage my own money, I sit on the boards of seven charities, I'm a mother - but now I'm thinking, "Wow, there's a whole big world out there and I want to learn to live it before I do anything else." '

I Can't Think Straight and The World Unseen are both out now on DVD