It's time you were married," said the man in the park this morning, while my dog tried to impregnate his without so much as a white wine spritzer. "Marry a rich man," he continued, "that way even if you're apart you'll be rich." Now, I don't take him particularly seriously - he also thinks girls with their bra straps showing are asking for it, and he has a curious objection to words that begin with vowels, such that he adds an H to them. But it's instructive, in any discussion of pre-nuptial agreements, to remember the model from which most of our prejudices derive: once you've married some sap of a man, he has to keep you for the rest of your life, regardless of any subsequent break-up or bad behaviour on your part.  Even in a time before women's wages crept up to approximate men's, this scheme rarely held sway. The person shelling out to a former spouse will be the person with the most money; and that person will also, inevitably, have superior legal advice.  Study after study has found that men who divorced in the 60s and 70s, a time when you could fairly assume them to be the greater earners, were far better off afterwards than their ex-wives would ever be. The fear of being skanked financially by your spouse, in other words, is irrational and always has been. But then, so's vagina dentata and it didn't stop us making a phrase out of it.  A related injustice against men is the sperm banditry whereby a woman will entice Boris Becker or Mick Jagger, say, into a sperm-yielding situation, have a child, then make him pay through the nose for the next 18 years, while she has a load of facials and laughs about him to all her friends.  That situation happens very infrequently indeed. I think it might have happened precisely twice - with Becker and Jagger - requiring as it does such a massive differential of income to make it worthwhile for the woman that only superstars need really worry. Yet these cases enjoy an awfully high profile, as if they were legitimate cautionary tales, and everyone should be on guard for a nubile schemer trying to make a fast buck.  Nothing, though, underlines the culture of inter-gender mistrust quite so well as the rise of the pre-nup. These are curious documents, signalling the financial intent of each party should the worst happen to their blessed union.  As such, they are wholly misleading, since they are entered into in the spirit of generosity, and consulted in the spirit of deep rancour, but they're probably fairer for that. Legally, they're pretty watery, since they operate only as guidelines for the judge, and are not binding.  A survey conducted by Smile, the internet bank, found 46% of respondents would undertake a pre-nup and would like it to be legally binding. Family lawyers report a 50% increase in these documents, though that sounds more dramatic than it is, given that the number was very small to begin with.  In America, where their use has been widespread for longer, their import has grown. In California, for instance, a pre-nuptial alimony waiver has always been overturned on the basis that it was against state law. You might just as well sign an agreement saying your spouse didn't care if you hit him on the head with a spade, and then attempt to use that as a murder defence.  In the recent Pendelton v Foreman case, though, the alimony waiver was upheld. State law no longer trumps the pre-nup in matters of spousal support, though I guess the spade defence would still be a bit ticklish.  The people who believe in marriage are assumed to be society's idealists. In the face of all evidence to the contrary, they believe a relationship can last forever. Even if they half-know it's not forever, they are prepared to suspend their disbelief in pursuit of happiness and excitement, just as you do when you go on holiday, even though in your heart you don't believe planes were designed to go up in the air like that. Friends and family will buy into it because they appreciate and indulge the grandeur of the gesture.  But the gesture is only grand because it is inclusive - excluding your income from the deal is like doing all the vows apart from the fidelity one. And the beautifully instructive thing about the pre-nuptial agreement is that it really does show modern marriage for what it is. It is not forever. It is not even a statement of romance, unless you can square with romance the suspicion that your beloved will one day squeeze you till the pips squeak. It is a party, like any other party, only with more poached salmon.  And while conservative opinion will blame just about anything for the institution's ignominious tumble - from the pill to divorce laws to "women's lib" - what really, finally did for it was money.