Initially it was all so romantic. Michael Douglas popped the question to his sweetheart Catherine Zeta Jones as the first sun of the new century rose over his luxury ranch in Aspen, Colorado.

In front of a party of close friends, he went down on one knee and proffered a 100-carat diamond ring, worth £500,000, by way of encouragement.

Now reality bites. Behind the scenes lawyers had been working for weeks to draw up a pre-nuptial contract for the couple, one British newspaper reported on Friday.

The agreement will protect Douglas's personal fortune - estimated to be as much as £180m - should the marriage fall apart.

It seems the star is keen to avoid the messy split with his first wife, Diandra, who is said to have walked away from their marriage with a £44m payout.

When it comes to Hollywood weddings, the pre-nuptial accord has become something of a formality.

Just ask Bruce Willis and Demi Moore, Elizabeth Taylor and Larry Fortensky, Rod Stewart and Rachel Hunter, Donald Trump and Ivana, Donald Trump and Marla.

When Carolyn Bessete wed John F Kennedy Jnr, she signed up to a sliding scale agreement designed to protect his $32m fortune.

It stated that were they to divorce in under three years, she would pick up $1m. Were the marriage to crumble between three and 10 years Ms Bessette would get $2m. Anytime after 10 years, and she could expect $3m.

This penchant for a spot of pre-nuptial housekeeping is all the more curious considering such contacts are by no means sacrosanct in the eyes the courts.

"In general, pre-marital agreements are no more enforceable under the American law than they are in the UK," says David Taylor, celebrity solicitor with London firm Finers Stephens Innocent.

Yet that obviously did not dissuade one unnamed couple from drawing up a 16-page treaty last March, that spelled out which petrol they should buy and who would do the laundry.

The fact that a prior agreement has been made shows a degree of intent and courts are likely to take this into account if called on in a divorce.

In Britain, the idea of linking love and loot in a legally binding contract is still looked down on.

Sandra Bowler, of Brides magazine, is pleased to say it's not an issue for her readers.

"If people elect to marry the aim of the game would be to commit to each other on a permanent basis. How can you do that if this matter of money has to be sorted out beforehand," she says.

"It really, really dints the concept of commitment."

Yet marriages do break down and while research shows the average cost of a wedding has rocketed to £14,500, divorce can be a far the more expensive option.

Which perhaps explains why the government is canvassing opinion on the matter.

Its discussion paper Supporting Families proposes the idea of a mandatory pre-nuptial agreement with a 50-50 split should the marriage break down.

The Law Society backs the idea but has recommended safeguards to take account of changing situations.

"The situation can change and it might be that if there are five children and the wife takes custody of them, she would deserve more money," said a spokeswomen. "It might mean a clause that says the contract should be reviewed every year."

While this is bound to make the romantics among you wince, the concept warrants a second look.

The Which? Guide to Getting Married says that some "find that discussion, or even making a written agreement, will help to focus their thoughts and highlight what exactly is involved when entering into marriage".

Christine Hayes of Wedding and Home magazine agrees. "[Contracts] may not seem very romantic but the advantage is that it gets the couple talking before the marriage about under what circumstances they would split up," she says.