Legend has it that on Queen Elizabeth's return from one of her lengthy foreign trips, Charles -- who was then about 5 and hadn't seen his mum for several months -- could hardly contain his excitement. As he bravely stepped forward to shake her hand, the monarch's first words to her firstborn were, ''No, not you, dear.'' Then she turned her attention to waiting dignitaries. Only after discharging her queenly duties did she enjoy a private reunion with her affectionate son.

Such stoically deferred family reunions aren't likely to be repeated in the next generation if Diana has anything to say about it -- and she does. Parenthood is her first priority, she has told friends; being a princess comes | second. She may consort with kings and mingle with movie stars, but those close to her say she is most comfortable -- and secure -- in her role as mother to princes William and Harry. In an aristocratic society in which nannies and governesses have historically played critical roles, Diana is a doting, hands-on, occasionally overindulgent mother who devotes an exceptional amount of time to her children. ''As a child, Diana was stuck in the nursery with a nanny,'' says Ingrid Seward, editor of Majesty magazine. ''I think she very much didn't want that for her children.''

Make no mistake, Diana has plenty of help with which to carry out her maternal mission. There are two 24-hour nannies, two detectives assigned to the boys and at least three footmen (think of them as male maids). Despite all that, Diana has tried to ensure that her boys be raised as ''normal children'' -- a somewhat naive undertaking, perhaps, given their birthright.

Give her credit for trying, though. From the start, she defied past royal practice -- and reportedly her royal mother-in-law's wishes -- by choosing to give birth to both William and Harry at St. Mary's Hospital in Paddington, with Charles present, instead of at Buckingham Palace. She breast-fed both boys for two months and installed them in nurseries within earshot of her bedrooms at Kensington Palace and Highgrove. (Royal gossip has it that after William's birth, she irritated his nanny at the time, Barbara Barnes, by clambering out of bed in the middle of the night to answer his cries, when the requirements of stiff upper lippedness demanded that he should have been trained to sleep through.) And unlike Queen Elizabeth, who spent months away from her children in the line of duty, Diana left protocol in tatters by toting 9-month-old William along on a six-week tour of Australia and New Zealand in 1983. Wills later became the first royal heir to attend nursery school and Harry soon followed, perhaps because Charles was tutored privately at Buckingham Palace until he was 8, and found it a lonely experience.

At times, Diana displays the anxieties of a guilt-ridden working mother. Now that they are in school (Harry, 3, at Mrs. Mynors' $2,600-per-year nursery and William, 5, at $4,300-per-year Wetherby pre-prep), Diana leaves the boys home when she travels but carries a silver-framed photograph of each of them and pines for them openly. She refuses to go on tour for more than three weeks at a time and fits a daily call home into her schedule whenever she is on the road.

When duty calls at home -- and it does almost constantly -- even the smallest separations are painful. On Harry's first day at Mrs. Mynors', Charles and Diana drove him there personally, while the detectives followed in a separate car; later, Diana cut short her morning engagement -- the opening of a dairy -- and sped back to Kensington Palace so she could be there when he came home. ''I was upset about leaving Harry,'' she told another young mother that day, ''but now I'm going to meet him, and I can't wait.''

She and Charles are determined to involve themselves in the children's school activities. Diana attends organized teas with the other mothers, subjecting herself to the inevitable gawking, and when Harry played a goblin in his school's Christmas pageant, Diana and Charles were there, grinning and applauding with the rest of the parents. When William's school held a sports day last June, Diana pleased her elder son by capturing the mothers' 50-yard dash -- and in a dress, no less.

Diana does nearly all the boys' shopping, keeping them trendily clad in clothing by Absorba, Benetton and OshKosh. Harry, of course, wears some of William's hand-me-downs, a routine in every family, royal or otherwise. Diana limits their TV viewing to after school; on Saturday the boys watch morning children's programs, including the old Flipper series, but violent shows are forbidden. Harry and Wills are allowed to gorge on potato chips and soda pop only at birthday parties; otherwise they must make do on a diet of chicken, salad, cooked vegetables, fruit and milk. They rarely go to restaurants, though Diana and a girlfriend recently treated Wills and Harry to a giggly, greasy meal at the American-style Chicago Rib Shack in Knightsbridge that left other diners nudging and gaping.

Like any normal brother team, Harry and Wills, born a mere 15 months apart, have a complicated relationship that is both loving and competitive, with William as captain. ''He would not be willingly nasty to Harry,'' says a palace aide, ''but he does like to be the one in charge.'' The aggressive William protects Harry; the thoughtful Harry adores William. But Harry, considered brighter and more independent than his big brother, intensely dislikes being compared with him. ''One day they were doing clay modeling,'' an indiscreet Mrs. Mynors' mum reportedly confided, ''and to motivate Harry a bit, he was told how good William had been at it. That did it. Harry threw the clay on the floor and refused to touch it for the rest of the day.'' Diana is aware of such sensitivities and makes a point of respecting them. ''She doesn't say to William, 'You should be more quiet like your brother,' or say to Harry, 'Get on with it, like William,' '' reports a palace observer. ''She treats them as completely separate people.''

When either of the royal kids throws a tantrum, no-nonsense nanny Ruth Wallace or her assistant, Olga Powell, often steps in to referee. Barbara Barnes, William's nanny for 4 1/2 years, left the family by mutual agreement in January 1987 for reasons that were never made public. Some say Barnes felt less the executive in charge of child rearing, as most British nannies like to consider themselves, than Diana's reluctant second-in-command. Others suspect Diana was wounded when William learned to say ''BaBa'' before he learned to say ''Mama.'' But the version given the greatest currency is that Charles and Diana believed that Barnes, who doted on William, wasn't strict enough, and that she resented the intrusion when Harry was born. (The Queen, for that matter, has been known to stick in her tuppenceworth about the boys' upbringing as well, and some say it was she who suggested a new nanny to Charles.)

The Waleses, perhaps eager for Wills and Harry to see how the other half lives, sent both boys on a top-secret outing last July to a working-class London neighborhood where they played with a group of children. There, a sharp-eyed little girl, who thought she recognized the future King, asked a detective what the boy's name was. ''His name's Roger,'' the detective replied. ''No it's not, my name is William,'' piped up Wills, blowing his own cover. Otherwise, the outing couldn't have gone better. ''A gerbil ran down my back and William grabbed it off,'' said playmate Anastasia Harrison, 11. ''I was very grateful.''

Despite Charles and Diana's attempts at fostering an illusion of ordinariness, both parents understand that the rich are different and royals even more so. Windsor children are taught early to know what is expected. Even before his third birthday, Charles had learned to bow before offering his cheek for a peck from ''Gan Gan'' -- his grandmother, the Queen Mother -- and never to sit in the presence of his grandfather, King George VI, without being asked. Harry and Wills are slowly becoming aware that they, too, are special. Masters of the Windsor Wave, they are old pros at mugging for lensmen. What child, after all, wouldn't delight in superstar treatment such as having a detective assigned to him daily? (This provoked one curious schoolboy to ask his mother, ''Why does William's dad come to school with him every day?'') On most Thursdays, Diana whisks the boys from school to a standing appointment for tea with the Queen, whom they call ''Granny,'' at Buckingham Palace; on Friday afternoons, they tend to go straight to their stately country home, Highgrove, for a private family weekend with Tigger (their Jack Russell terrier), Bunny (their rabbit) and a handful of servants (the nanny, chef and butler among them) imported from Kensington Palace.

The perquisites of royalty do not end there. The boys have a pony apiece and luxurious toys (the Jaguar company built a miniature electric version of an XJ-S Cabriolet for William's second birthday, reportedly worth $40,000) and are sometimes allowed to visit department-store Santas before commoners do. (''What are you doing here?'' William is said to have once asked the Selfridges' Santa. ''We saw you at Harrods last Friday.'') And, during August for the past two years, Harry and Wills have joined their parents in Majorca for a Wales family visit with close friends King Juan Carlos and Queen Sofia of Spain; then it was on to Scotland to visit their grandmother at Balmoral.

As happens with their parents, every known detail of the boys' childish indiscretions is widely reported by the press or through the grapevine. When boisterous William was denied the honor of blowing out the candles on the birthday cake at another little boy's party, he shouted, ''When I'm King I'll order my knights to come and chop your head off!'' Parliamentary democracy may not have trembled, but the tabloids were alert in an instant. When Harry ran away from teasing classmates at recess and hid behind the playhouse at Mrs. Mynors', the racy News of the World was quick with the bulletin. Diana, understandably, has serious misgivings about such unabashed prying. When photographers once tried to get a photo of young William leaving Kensington Palace, she reportedly rolled down the window of her car angrily and scolded, ''Leave him alone! Alone, do you hear! How would you like your children to be treated like that?''

Both Charles and Diana, for somewhat different reasons, are instinctive defenders of home and family. Despite his mother's long absences and his father's indifference to small children, Charles once said of the Windsor clan, ''We happen to be a very close-knit family. I'm happier with my family at home than anywhere else.'' Diana, on the other hand, was stung when her mother, Frances, ran off with London wallpaper magnate Peter Shand Kydd when Diana was only 6, abandoning Diana's father, Lord Spencer, and their four children. A nasty divorce followed, and Diana, says Penny Junor, author of last year's biography Charles, ''seems determined to give her children the family life she never had herself.'' That may also explain her reluctance to discipline her boys. Says one palace watcher: ''She has to really be pushed before she will tell them off.''

Charles, known as ''Daddy,'' is a softy as well, though he seems less indulgent in public -- perhaps because he knows so well from his own experience the high standard of behavior that his boys will be held to. Behind palace doors, however, he is known to be mad about the two of them; when they were younger, he often delighted in feeding and bathing them. (Of late, however, his image as a dutiful dad has been tarnished somewhat by his extended absences from home. Insiders are worried that these absences may be hurting his relationship with his sons. ''It seems to be that he's with them when it suits him, not when it suits them,'' says one palace source.)

For the moment Charles and Diana seem content with the delicate balance they have achieved between the obligations of royalty and the rigors of parenting. They would reportedly like to have three children; Di has made no secret about wanting a daughter and, not insignificantly, a potential shopping partner. Whatever the gender, the next Wales bundle, inevitably caught between the public and private rigors of royalty, will have Diana, a loving mother and a staunch protector, in his or her corner.

BOX: NOW PLAYING WILLIAM THE BRASH

When Prince William stood at his mother's side at a Kensington Palace reception for international fashion writers last March, his surprise appearance was a smash hit by default -- he didn't embarrass anybody.

Clad in a white shirt and red silk shorts, Wills, who turns 6 on June 21, politely shook hands with 180 dignitaries. Mom patted him on the head and then hugged him before whisking him off to bed. ''It was nice William could be with me tonight so he can see what I do,'' said Diana. ''It is good practice for him, shaking hands, although he did get a little fed up towards the end.''

It could have been worse. The royal family has taken to holding its breath whenever William leaves home. His old tricks -- setting off security alarms and trying to flush his father's handmade shoes down the toilet -- were once considered signs of spirit, but no longer. ''That was cute at 2,'' says one royal watcher. ''But he is the future King and has to one day start acting as such.''

The Queen would no doubt agree. Only last summer she scotched plans to bring William to the Braemar Games, a ritual royal outing near Balmoral, because he couldn't be trusted to behave. Even Di's dad recently confessed that when his grandchildren get together, ''. . . if there's ever any trouble, then it's always William who's the ringleader.''

The British tabloids have had a field day with William's tantrums. Last year the Sun reported that soldiers in the Royal Highland Fusiliers regiment had complained of being bossed around by ''the cocky little brat,'' who threatened to fire them and had started screaming when they ignored him. Charles is trying to spend more time counseling his elder son, although his patience sometimes wears thin. Last January, during an outing at Highgrove, William kept complaining that his hands were cold. Snapped Charles: ''I told you to bring gloves when we left the house, and you didn't, so shut up.''

William's school manners, too, occasionally leave something to be desired. Three sets of parents at Wetherby considered pulling their boys out after Wills had a scrape with two of them and threw a chair at a third. He also reportedly began a brouhaha at a friend's birthday party in a dispute over the menu. ''He screamed that he hated the food -- sandwiches, jelly ((Jell-O)) and ice cream -- and threw it around the room,'' claimed a nanny who witnessed the scene. When another nanny tried to get him to clean up the mess, he reportedly said, ''Do you know who I am?'' before sulkily cleaning up and clearing out in disgrace.

Diana, naturally, is concerned with such boorishness but could be described as exceedingly tolerant. She seems in no hurry to smooth any but the roughest of Wills's rough edges. ''She wants to see him run loose, as she knows that he will be restricted later on,'' says one observer.

Diana is also determined to teach him the value of money -- though he is unlikely to carry any as an adult -- and to that end gives him about 55 cents a week in pocket change. She still remembers the time Charles stood in line to buy snacks for his teammates after a polo match, ordering three smoked salmon sandwiches, four teas and a chocolate cookie, and tried to pay with a one- pound note (about $1.85).

Perhaps William's problem at the moment is that he knows that he is special but doesn't yet understand what is expected. His father knows too well that it won't always be this way and that the implications of the line of succession will eventually make themselves felt. ''I think it's something that dawns on you with the most ghastly, inexorable sense,'' Charles once said. ''I didn't wake up one day in my pram and say, 'Yippee!' ''