MP Malcolm Bruce is marrying a woman half his age. The happy couple say they don't mind the gap, but Virginia Ironside sees plenty of pitfalls ahead
"IF they say I'm too old for you, Then I shall answer `Why, sir, one never drinks the wine that's new, the old wine tastes much nicer!"

So runs the song of the old roue in Sandy Wilson's The Boyfriend. But is it true? On Saturday, Malcolm Bruce, the 53-year-old Liberal Democrat Treasury spokesman, marries 26-year-old Rosemary Vetterlein, a girl young enough to be his daughter. Indeed, the difference in their ages is even greater than the age of the MP's youngest child, 21-year-old Caroline. They claim that the age difference hasn't even crossed their minds. Everything's going to be fine.

But there are enormous disadvantages to marrying an older man. For a start, if Rosemary's going to have children, their father will be the oldest dad in the playground, and by the time they're in their teens he'll be in his seventies. There's also the problem of an older partner going gaga, as my grandmother used so graphically to put it, and the poor wretched younger one having to play nurse for years in his or her old age.

Added to this, the younger one's parents will probably be getting bit rocky, too, and he or she might end up with three oldies to look after, as well as teenage children, a bit much for anyone, particularly if the carer is a woman who's going through the menopause as well. It's one thing to marry a father figure who takes care of you, but it's another to end up with a dribbling, cranky old wreck who you have to look after.

True he might conveniently die of a heart attack at 80, having been a spry old thing up to the day he dies, but however full of beans he is, if he's like most men he'll be losing interest in sex just at the time when many women feel most sexually free, and another rather crucial part of the marriage may be going down the drain.

And an older woman and a younger man? (a state of affairs that is becoming increasing common, according to Denise Knowles of Relate) Same applies. But there's the added disadvantage that the older woman might not be able to have children, and since there's nothing most men like more than reproducing themselves - it's in their jeans, as the actress said to the bishop - there may come a time when he starts looking around for someone who's fertile.

"I feel he is destined to be a father and would make the most wonderful one. And as I wouldn't be likely to give him children, it wouldn't be fair to marry him," says Jilly Johnson, the Sun's first topless Page Three girl turned author, now 44, who is dating Chris Sheasby, Harlequins rugby star, some 13 years younger.

Infertility is one of the reasons that the relationships between older women and younger men are often so disapproved of by families. "The parents want grandchildren, and hate the fact that the woman involved may already be a grandmother herself," says Denise Knowles of Relate.

"Added to this is the fact that the woman may be closer in years to the man's own mother and that makes the father feels threatened, because he subconsciously wonders if his own wife might not be looking for a young man, too."

She puts the increase in older women/younger men relationships down to several factors. Many women are no longer old drudges in their fifties, but fit and with a great deal of energy and zest for life - and experience which young men find very alluring. A lot of younger women are so wrapped up in their careers that they don't have the time for relationships that an older woman may be prepared to nurture.

Chris Sheasby says "age is just a number" and refuses to face the problem, but Jilly's sensibly quite worried. It's exactly the maturity and good sense that attracts her to him - as well as the other obvious attributes - which makes her pause before jumping into anything more permanent.

He does bring out the motherly instinct in me which I find quite confusing," she says. "He's still just a boy." The Oedipus story was echoed by actor Alfred Molina, who married actress Jill Gascoigne, 16 years older. He says: "I think men like to be looked after. After all, most men go from a home where they're looked after by their mothers to a home where they're looked after by their wives."

There are two other factors that are often ignored. One is that if you marry someone extremely young, they're bound to change more than if you marry someone a bit older. Jerry Lee Lewis married a 14-year-old in his middle age, but the girl he married at 14 would not, at 24, be the same person. Secondly, there's the question of social generation. Jilly Johnson and Chris Sheasby will have shared interests in rock music, and both will know about youth culture, women's rights, and the other trappings of post- Sixties society.

But a woman of, say 50, who gets together with a man of 70 will find there are huge cultural differences. He was brought up in the Thirties and Forties. He will have been in the War. However nice and kind he is, his friends may well be old soldiers and the post-Sixties generation and the woman's movement will baffle him.

Yet marriage with huge age gaps can often work extremely well, as long as everyone's aware of the pitfalls. "How successful relationships with big age differences are depend on how couples go into them," says Denise Knowles. "If a woman is looking for a father figure and a man is looking for a mother figure, they can work for a short period of time, but then one or other gets fed up with the role. But they can work very well."

Bruce Forsyth is twice as old as his wife; Oliver Reed is 26 years older than his. As the song says: "It's never too late to have a fling, for autumn is just as nice as spring. A gentleman never feels too weak, to pat a pink arm or pinch a cheek.And it's never too late to fall in love."