Once upon a time there were two princesses. The older sister was good and always did the right thing. She had a wonderful smile. When she grew up and became queen, she was going to single-handedly bring about a second Golden Age. Just like the first queen of the same name. Only better.

The younger sister was petite, shapely, smiled a lot and was absolutely stunning. All she had to do was be lovely, and, as one of Stephen Sondheim’s heroines sings in “A Funny Thing Happened on the Way to the Forum,” she did that extremely well. She joked and flirted and stayed out late and smoked and was really bad.

The good one went on to become queen but did not produce the expected miracles. She lost whatever style she had and wore stiflingly dull clothes. She loved her horses and dogs and sat at soldierly attention during the world’s dullest speeches. (She still had a wonderful smile.) As for the younger sister, she got drunk and fat and came to a bad end.

Now the elder sister, Britain’s Queen Elizabeth, is about to celebrate her diamond jubilee. “Sixty glorious years!” they said when Queen Victoria achieved this same feat in 1897. The bands played, the Union Jack flew, and millions cheered. They will do so again, no doubt, to celebrate an institution so curious and anachronistic that its like scarcely exists anywhere else. That’s because, it is said, Brits love a good show and are sentimental about the royals, and lots of Elgarian pomp and circumstance reminds them of departed glories.

In the interest of full disclosure, this reviewer should state that she was born and grew up in England, has since become an American citizen and is completely convinced of the obsolescence of the monarchy, if only in sympathy with those who have to go on writing about it. How can one possibly argue in favor of it without sounding fawning, deferential or even hagiographic? How can one attempt to show the human side without descending into banalities?

’Elizabeth the Queen: The Life of a Modern Monarch’ by Sally Bedell Smith (Random House)

Such thoughts arise in response to two biographies timed to coincide with the diamond jubilee celebrations. Does it help to know that Elizabeth II wears an old coat and rubber boots, keeps her cereal in plastic containers and has compared herself to Miss Piggy? Do we really need this?

There are, of course, paths to understanding the emotional forces that have molded the queen, although neither Andrew Marr, author of “The Real Elizabeth,” nor Sally Bedell Smith, author of “Elizabeth the Queen,” seems interested. This is peculiar, because even a surface examination finds the royals divided by the great chasm between duty and passive (or not so passive) rebellion.

What about Queen Victoria, who kept her successor, the rakish Edward, waiting until he was old and gave him nothing to do, so that he was obliged to fritter his hours away on wine, women and song? Fast-forward to a more recent heir, Edward VIII, the handsome lightweight who gave it all up for an iron-willed charmer and wandered through cafe society looking like a man in lengthy and remorseful contemplation of the path not taken.

What about Elizabeth’s emotionally wounded father, George VI, whose stammer almost destroyed his life, as we are reminded in the recent film“The King’s Speech”? What about his wife, who was nothing like the modest and retiring figure depicted in that film, but a good-time girl who began every morning at 11 with her first drink, danced all night and was, as one of my biographical subjects, the art historian Kenneth Clark, discovered, a relentless flirt?

And what about Elizabeth herself, who, when reunited with her firstborn, the 5-year-old Prince Charles, after months away on tour, solemnly shook his hand? What about her choice of husband, the dashing and opinionated Philip, who showed an alarming tendency toward foot-in-mouth disease? What about three of her four children, with their dreadful divorces and those repellent details? Who are these people?

The idea of a dysfunctional family trying to keep up appearances might be a valid approach, but it does not get much attention in either of these biographies, which both claim to be telling the true, real, “intimate” story of Britain’s enduring monarch. Marr, a BBC broadcaster, has a weakness for the kind of magisterial assertion that contaminates television documentaries.

Elizabeth is real, he writes. She loves people. She is calmly confident. She moves with the times. But she holds fast to eternal verities. She is magnetic. “The Queen has a force-field aura. . . . An appearance by the British monarch creates an atmospheric wobble of expectation, a slight but helpless jitter. When she turns up, people find their heart rate rising.” In Marr’s view, the public’s adoration is “sparklingly, crystal, clear.”

While slathering on the compliments, he feels free to offer his advice: The monarch should evolve into the “nonexecutive chairman of the national company.” There is something irritatingly condescending about his efforts to be matey, as with the Miss Piggy revelation. Oh yes, and by the way, the young princess had a great pair of gams.

One turns to the biography by Sally Bedell Smith, which shows evidence of much searching for new material, even if this often turns out to be inconsequential. Take, for instance, Her Majesty’s mild complaint that, on commonwealth tours, she has to sit next to boring mayors.

No one, after all, wants to risk Buckingham Palace’s displeasure with more meaty revelations, so these tend to be of the “Was I ever embarrassed!” variety. Sir Cecil Hogg, one of the royal doctors, confessed to palpitations when he had to peel back the royal bedclothes to listen to the royal lungs.

Then there is the whole subject of divorce, which defeated the Duke of Windsor. The same taboo bedeviled Princess Margaret, who had the bad luck to fall in love with Peter Townsend, her father’s equerry, who was divorced. Since Queen Elizabeth is also head of the Church of England, which at the time forbade divorce, Margaret was obliged to send him packing or risk being cut off from the Royal Treasury, a fate too terrible to contemplate.

One wonders how Margaret felt about the subsequent string of royal divorces. If she and Princess Diana had something to say about all that, it is a safe bet that it will never be published. And when the time came for Margaret to divorce her own husband, Lord Snowdon, she did that, too.

For the most part, Smith takes on the role of royal apologist, one that somehow creeps into the prose of everyone, even American authors, who gets within several thousand miles of Buckingham Palace. The awe of it all causes such writers to dress up their subjects with wholly speculative virtues and give the paean of admiring comments a quick nip and tuck if they are not sufficiently sycophantic.

For instance, when the royal photographer, Cecil Beaton, goes to a Buckingham garden party, Smith cites his admiring conclusion that the queen and her subjects are salt of the Earth. But the author omits to mention (as noted in Beaton’s unexpurgated diaries) that he found the flowerbeds garish and the women’s clothes appallingly drab, and stated that the queen was as dowdy as the rest, wearing a suburban straw hat and coat and carrying a “terrible” white handbag.

When the Diana problem became too large to ignore, did the queen’s comments help or hinder? We don’t know, actually, but Smith is sure that the whole issue was her son’s wife’s neurosis. Whatever could Diana want? Didn’t she have it all? What about the queen’s refusal to cut short her Balmoral holiday and return to London after Diana’s death in 1997? Well, you see, that was because the queen wanted to spare her grandsons further pain, Smith explains. Not showing emotion is, of course, good form in Britain, but this felt more like icy indifference: Stoicism has reached its apogee.

What, then, are we to make of everybody’s granny with her unflattering hairstyle and frumpy hats? One can only conclude that in her case, birth, training and ceaseless indoctrination have worked all too well. Queen Elizabeth has become the cardboard figurehead that the British public expected. Adored — well, that’s something else. At least she is still there.

So she will be cheered and feted, and why not? She deserves an A-plus for those decades of steely self-abnegation, those retorts bitten back and that teeth-jarring boredom. Here’s hoping, as seems more likely, that William and Kate will turn out to be “real” without even trying. Their roles are not likely to become easier. As Prince Philip remarked, if people knew all that the job required, why would anyone want it?

Meryle Secrest is author of numerous biographies in the arts and in 2006 was awarded the National Humanities Medal. She is currently working on a biography of Italian fashion designer Elsa Schiaparelli.

THE REAL ELIZABETH

An Intimate Portrait of Queen Elizabeth II

By Andrew Marr

Henry Holt. 349 pp. $32

ELIZABETH THE QUEEN

T he Life of a Modern Monarch

By Sally Bedell Smith

Random House. 663 pp. $30