He loves you (yeah, yeah, yeah)

The news that Heather Mills McCartney is pregnant will come as no surprise to those who have watched her whirlwind annexation of Britain's Number One national treasure. For, in truth, Heather has taken over Sir Paul McCartney in much the same unstoppable way that his former band, the Beatles, once used to take over the charts. And, with a baby now on the way, she can claim to have "gone gold".

The announcement doubtless will have been expected by McCartney's grown-up children ever since he presented them with a stepmother of around their own age, a little less than a year ago. Despite their protestations to the contrary and stapled-on smiles, it seems plain that Stella, Mary and James McCartney "long for yesterday", when he was married to their mother Linda.

Impending motherhood could not be much better timed for Heather, who has not enjoyed an unqualified good press since winning Sir Paul, despite being still recognised as an indomitably courageous character, undaunted by the loss of part of her left leg when she was 25, and a tireless worker for charity. It is only three weeks since a Channel 4 television-documentary challenged several-aspects of the brutally hard life she claims to have lived before she was famous.

But the former Beatle she has wed is real enough, as is the beneficial influence that many believe she has had in blowing away the clouds of sadness that hung around McCartney following Linda's death in 1998.

In return, he defers to her in a way he never did even to Linda. No one else in his whole career has been allowed to give him "notes" on his stage performance each night, as Heather does now.

Having attained such influence, it can hardly have been difficult to persuade him to re-embark on the long and winding road of parenthood at the age of almost 61.

Being almost a billionaire will of course soften many of the hardships faced by workaday dads, especially those who find themselves faced with parenthood's demands at an age when being awoken in the night or heating bottles at dawn is no joke.

He could, so easily, employ roundthe-clock nannies - and what new parents sometimes wouldn't wish for such relief ? But, rich and starry as he is, I suspect Sir Paul will be a thoroughly hands-on parent.

As biographer of the Beatles, there are many aspects of his character and public persona I may question. I may call him, in many respects, a wasted talent who has abandoned the glorious creativity of his early Beatles compositions, such as Eleanor Rigby and Yesterday, for middle-of-the-road pap like Mull of Kintyre and his cover version of the TV soap Crossroads' theme.

But I cannot deny that as a parent he has been an outstanding and unqualified success.

The family life he established with Linda after the Beatles' break-up in the early 1970s won admiration from anyone who had ever seen the usual fate of rockstar kids, who tend to be simultaneously over-indulged and neglected. Indeed, though Linda had initially been far more unpopular than Heather is now, she won respect during their 29-year marriage as a devoted wife and mother.

Selfish and self-centred though McCartney might be as a performer, he proved a model father, putting in the same hard slog in the nursery that Linda did, bathing and changing his babies each night and singing them to sleep.

As someone who went through it all myself in early middle-age, I now know the drudgery was worth it for the incredibly intimate relationship it forges between you and your child. The hardships are physical - but the rewards are spiritual.

I feel absurdly pleased with myself for having done it all just once. McCartney did it three times, and still had father-love left over and to spare. By a previous marriage, Linda had a daughter - ironically also named Heather - whom he has always treated as his own. She, at least, of his four existing children, should know that it's worth giving stepparents a chance.

In between touring with their band Wings, the McCartneys lived quietly in Sussex, at a house which - in those sunnier, more secure times - did not have security gates or, indeed, any gates at all. Far from being the usual pampered rock-star brats, Heather, Stella, Mary and James were sent to local state schools and dressed no more expensively or showily than any of their classmates.

From her couture eminence now, Stella McCartney may joke that her father was a skinflint towards her and her siblings when they were children.

But all three show the benefit today in being unspoilt and thoroughly civilised. Stella in particular has owed little of her huge success to being called " McCartney" and likes to characterise herself as "just a working-class broad" as if she's hauled herself up from some Liverpool tenement rather than from a multimillionaire's Sussex estate.

All Linda's children seem to possess their late mother's innate restraint and good taste. What seems to appal them most about Heather is the unabashed gutsiness that others so admire - for example, that recent moment on American television when she whipped off her prosthetic left foot and waved it under the nose of chat-show host Larry King.

Under Heather's influence, McCartney has seemed bent on rejuvenating himself, dyeing his hair, wearing tooyouthful clothes and attending " glamour" functions that Linda would have considered far beneath him. For him to opt for fatherhood again, when he's already a grandfather, will inevitably be seen as part of the same process.

In a song on the Beatles' most famous album 36 years ago, he playfully speculated on what life might be like "when I'm sixty-four". Before that anniversary comes, I suspect, the second Lady McCartney may have further surprises in store for him.