The divorce case between Sir Paul McCartney and Heather Mills may have garnered all the headlines last week, but lawyers said the less high-profile Crossley case could have more far-reaching consequences for wealthy couples.

Last week, “serial divorcée” Susan Sangster dropped her case against her estranged husband Stuart Crossley. The couple had signed a prenuptial agreement following a whirlwind romance, stating that they would not claim on each other’s million-pound estates in the event of a divorce.

However, when the marriage failed after 14 months, Sangster, who has been married three times before, argued that the agreement was null and void because Crossley had failed to disclose “tens of millions” held in offshore accounts.

However, last week she decided not to go ahead with the claim after the Court of Appeal upheld the agreement in December.

Lawyers said the case had strengthened the legal position of prenuptial agreements and said all wealthy couples should take one out – or a postnup if they are already married.

Alex Carruthers, at Hughes Fowler Carruthers, a London law firm, said: “This case will make it easier for judges to uphold prenups, which are still not legally binding in this country, in the future. I do not think they will want to relinquish their ultimate discretion to disregard an agreement should they see fit, but the wind is certainly blowing in that direction.”

Two out of five first marriages and seven in ten second marriages now end in divorce – and payouts awarded to those leaving wealthy spouses have soared in recent years.

Women are three times more likely to file for divorce than men, often due to infidelity or abuse, and the number of oversixties splitting has soared in recent years – by 48% since 1991.

Unsurprisingly, those who have had their fingers burnt are much more likely to insist on a contract when marrying again.

Suzanne Kingston at Dawsons Solicitors, said: “I would advise wealthier couples to take at least preliminary legal advice on whether or not to have a prenuptial agreement drafted. There is no doubt people are now more inclined to enter into them, especially when they have been married before.”

McCartney may well rue the day he decided not to make Mills sign away her right to a slice of his substantial fortune. It is thought she could end up with around £40m.

And this is by no means an isolated case. Golfer Colin Montgomerie’s wife Eimear got an estimated £8m when they divorced, and Sangster has been awarded £18m in previous divorce settlements.

The law on division of financial assets used to ensure only that the “reasonable needs” of the financially weaker party – usually the wife – were met as a result of the settlement. But the situation changed in 2000, when Pamela White, a former farmer’s wife who had worked in the family business and felt she was entitled to half the farm as a result, took her case to the House of Lords.

It decided that the Court of Appeal had been misinterpreting the law for 25 years and ruled that where there were assets in excess of both parties’ needs, it was wrong to limit a wife leaving a long marriage to provision for her “reasonable needs”.

Carruthers said: “The replacement of the reasonable-needs measure by the woollier concept of ‘fairness’ has worked in many wives’ favour. In Sangster’s case, however, she had sufficient wealth to cover her reasonable needs already.”

If you are considering signing a prenup before tying the knot, it is worth remembering that these contracts are still likely to be ignored by the courts in cases where unmentioned children are involved, because their interests are always put first.

To improve the chances of a prenup being recognised, both parties should take independent legal advice before signing and for the final version to be approved by both parties at least 21 days before the wedding to prevent concerns about one party coercing the other.

Lawyers representing couples who decide to take out prenups recommend full financial disclosure as the contracts are more likely to be recognised by a court.

One other way to make agreements seem fairer is to include a clause making it possible to change the terms after a certain time, or on major events such as the birth of a child.

For husbands and wives who are concerned about the division of assets should their union come to an end, there is the option of signing a postnuptial agreement.

“Postnuptial agreements are not as popular because there are fewer circumstances in which both parties will agree to draw one up,” Carruthers said. “But if, say, the wife’s father said he would buy them a £2m house, provided she kept the property in the case of divorce, both parties might feel it in their interests to sign a postnup.”

As with prenups, however, care must be taken to show that both parties are entering into the agreement freely.

“In one recent case, the postnuptial was disregarded because the husband was found to have pressured his wife to sign it,” Carruthers added.

A wedding is not a prerequisite for a couple to sign a financial agreement, either. So-called cohabitation contracts, which work like prenups for unmarried couples, are also becoming more popular.

More than 2m couples now live together in Britain without being married and family lawyers point out that it is even more important for couples in this situation to take action because they have little automatic legal protection.

Mary Webber of Advicenow, a legal-rights website, said: “Unless cohabiting couples make arrangements to protect their rights, and the rights of their partner, their worst nightmares could come true.”

As with prenups, there is no guarantee that cohabitation contracts will be accepted by the courts. However, setting out who owns what, as well as what contributions you plan to make towards the rent or mortgage repayments, should help you to divide your possessions if your relationship does founder.

CONTRACT TIPS

— Make the arrangements as fair as possible. The courts will throw out agreements they consider unreasonable.

— Ensure that both parties take independent legal advice and that the agreement is signed at least 21 days before the wedding.

— Do not try to hide assets. Courts are less likely to take an allow an agreement if either party failed to make full financial disclosure.

— Make provision for any children who predate the marriage and write in procedures that will be followed if you have any more. This could be in the form of an automatic review every time a child is born. You may also want to write in regular reviews.

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