The monarchy is secure if Kate got a behaviour prenup

‘Of course,” said she. “Whatever ‘in love’ means,” said he. These were the answers given by Lady Diana Spencer and the Prince of Wales in answer to a television interviewer asking whether they were in love, soon after their engagement. It should have been obvious right then that they appeared to have very different views about what was going on between them. In retrospect it is clear that what they urgently needed was a prenuptial agreement outlining what they understood about their marriage and its obligations.

Had each of them better recognised the motives and intentions of the other, by forcing everything out into the open in a carefully considered prenuptial agreement, they might have avoided a great deal of misunderstanding and misery all round — and grave damage to the monarchy as well. Watching the idyllic and very different wedding of their son William to Kate Middleton on Friday, I found myself hoping very much that the new Duke and Duchess of Cambridge had been wise enough to make a prenuptial agreement, as some of the media have speculated.

Prenups, as they are now called, are usually about money and what happens to it in the event of a divorce. While not legally binding here, they are increasingly likely to be taken into account by the courts since a ruling last October in which the Supreme Court in London upheld the prenuptial agreement of a German heiress, after her divorce. It is, of course, good to make clear where the money goes in the event of separation and to lay down various other practical conditions, both of the marriage and of any divorce.

After all, marriage is among other things a contract, and those entering into a particular marriage ought to be aware of the particular terms of that contract. So I favour prenups for practical reasons. They concentrate the mind in advance on subjects over which desire and romance would prefer to cast a veil and they can, insofar as they are enforceable, dispel doubt and mistrust and bitter squabbles when things go wrong.

I am also in favour — even more in favour — of prenups for emotional and moral reasons. Marriage is meant to be for life, for richer for poorer, in sickness and in health, to love and to cherish and for most of the purposes detailed in the beautiful Anglican wedding service. But such is the confusion surrounding marriage these days that people don’t actually agree on what it means or even know that they differ on important points. Does one sexual peccadillo mean instant divorce? Do children come first, or does the hungry heart? How much time does each person need to have to himself or herself? What compromises can be reached about parents-in-law or between careers? What does each person think is unacceptable behaviour? And what matters most to each person? This is something many people clearly don’t consider enough before getting married. Recognising such things in advance might help to make marriage a better, more emotionally binding contract.

The late Princess of Wales succeeded in promoting the narrative, and getting a lot of sympathy for it, that she was a young innocent, very much in love with Prince Charles, who was shocked and horrified to discover that marriage for him was very different. Whether or not it began for him as a marriage of reason to a suitable girl, or whether he tried to make it a romantic, companionate marriage, it soon turned into something more old-fashioned — a traditional upper-class arrangement, still favoured by many people of his class and age and certainly by many of their parents, in which divorce was pretty much out of the question and sexual infidelity was not reason enough to end an otherwise tolerable marriage.

I never quite believed that Diana had no idea of what she was getting into. Her noble family had been courtiers for hundreds of years. It seemed to me that anyone from her background — her sister had even dated Charles — must have known that divorce was unthinkable and therefore that by taking on the “intolerable privilege” of marrying the future king, as the late Queen Mother called royal life, she was accepting that she might have to put up with a lot that an ordinary person might find intolerable.

Any ordinary person can decide to abandon a marriage that goes wrong in that way, or in any other. But a royal bride or groom cannot or, rather, certainly should not. The marriage of Kate and William, and the contract it self-evidently contains, is — like Westminster Abbey itself — a Royal Peculiar. It would be disastrous for the monarchy, as well as for the royal couple, if their marriage were to end in divorce. Almost uniquely, their union has to survive, if necessary, the loss of passion and the loss of love — both emotions which are not in the power of duty to command.

Duty can, however, command all kinds of virtues which could ease the pain of a failing relationship and the frustrations of an intolerable privilege. And these are things which could be worked out in a royal peculiar prenup, or an immediate postnup.

What are needed are kindness, forbearance, tolerance, courtesy and affectionate solidarity. A list of marital misdemeanours could be drawn up which each would promise to avoid or atone for — for a royal couple the ones that come immediately to mind are hogging the limelight, competing with each other in any way, secretly briefing the press, getting high on deference or infected with red carpet fever, allowing separate cliques of courtiers or advisers, resenting each other’s time away or other interests, or neglecting one another.

So would letting either family come between them. Other scenarios should be clearly considered. If adultery is ever permissible, given the impossibility of divorce and the unreliability of passion, under what terms is it intolerable — when it is very public, for instance? On their wedding day William’s and Kate’s radiant happiness must have touched even the most hardened of republican hearts. Outsiders cannot claim to know them at all, but it truly does seem that they combine maturity and wisdom with an enduring love for each other. That love has been tested in many ways over many years and if any couple could make a success of married life as a future king and queen, perhaps they can. Many millions of people are hoping so and wishing them every happiness in their Royal Peculiar marriage.

minette.marrin@sunday-times.co.uk