In 1895, the year that Consuelo Vanderbilt married the Duke of Marlborough, the Los Angeles Herald Examiner wrote that some $200 million had “gone away from these shores” in the form of heiresses’ financial worth. In 1908 a play entitled The Stronger Sex, staged at Weber’s Theater on Broadway, took as its subject matter the pursuit of a rich girl by fortune-hunting noblemen, a practice that, according to one critic, “has become a public scandal.”

The practice was not really going anywhere—between 1933 and 1964 Barbara Hutton would marry five European aristocrats—but as a fashion, an industry even, it was on the way out. “We have heard that story before—till we can barely hear it patiently again,” wrote The Times in 1917 of a musical comedy at the Shaftesbury Theater, whose central character was an American heiress pursued by an impoverished European aristocrat, blah, blah, blah.

Consuelo, then the Duchess of Marlborough, 1905.

In Britain, the scions of upper-class families were not chasing heiresses but being obliterated on the battlefields of France. And in the United States, even before the outbreak of war, the Gilded Age had given way to something more sober.

It had reached a symbolic high point on an evening in 1897 at the Waldorf Hotel, where the Bradley-Martins held a costume ball whose $369,000 cost would, it was estimated, have fed almost a thousand families for a year. “We are the rich,” declared a wisely anonymous guest. “We own America. We got it God knows how, but we intend to keep it if we can.”

The scene within was, as so often, purest Versailles. Defying hubris, some 50 women came dressed as Marie Antoinette; in the case of Caroline Astor, with the addition of a tiara worth $200,000. The hostess, Cornelia Bradley-Martin—“so ablaze with diamonds from head to foot that she looked like a dumpy lighthouse”—wore a costume referencing not one but two doomed queens: she was dressed as Mary, Queen of Scots, and her ruby necklace, bought from the recent sale of the French crown jewels, had actually belonged to Marie Antoinette.

“We are the rich. We own America. We got it God knows how, but we intend to keep it if we can.”

To call this event tone deaf would be quite the understatement, given that it took place at a time of depression, the “Panic” as it was called, which had begun in 1893. It was not on the epic scale of 1929, and certainly it did not affect the 1,200 guests at the Waldorf. In the New York beyond Fifth Avenue, however, the Panic led to the opening of soup kitchens and sent unemployment for a time as high as 35 percent.

The new century brought the election of Theodore Roosevelt, for whom the New World aristos were “malefactors of great wealth,” whose power should no longer be absolute. “There is not in the world,” said Roosevelt, “a more ignoble character than the mere money-getting American, insensible to every duty, regardless of every principle, bent only on amassing a fortune, and putting his fortune only to the basest uses. These men are equally careless of the working men, whom they oppress, and of the State, whose existence they imperil.” That was telling them; as was this, in 1907: “The life of mere pleasure, of mere effortless ease, is as ignoble for a nation as for an individual.”

Barbara Hutton, who between 1933 and 1964 would marry a whopping five European aristocrats, at a ball at the Grosvenor House, in London.

Consuelo Marlborough—who had recently separated from her husband—was starting to agree. So was her mother. Now these women were hearing a new clarion call: the one that re-invented that totemic word “social,” by attaching it to hitherto alien terms such as “responsibility” and “conscience.”

Consuelo became deeply engaged with charitable work, especially in relation to mothers and children. The down-to-earth help that she gave to the Blenheim tenants—turning up at their homes with coal, blankets, even a pig—earned her the name “the Angel of Woodstock.” Easy to say, of course, that this was easy for her to do; nevertheless, she did it.

Consuelo was not the first to play the Lady Bountiful role—it was an aspect of noblesse oblige—but the point was that philanthropy was now acquiring a political aspect. The delivery of sacks of coal was kindly and direct, welcomed for precisely that human touch. Better yet, however, would be if the coal could be afforded in the normal way of things, if charity and gratitude were no longer needed.

Now these women were hearing a new clarion call: the one that re-invented that totemic word “social,” by attaching it to hitherto alien terms such as “responsibility” and “conscience.”

In 1917 Consuelo was elected as a candidate for the Progressive Party in the London County Council elections, standing in the impoverished area of Southwark West. Her slogan was “Vote, Vote, Vote for Mrs. Marlborough.” A brief piece of Pathé film shows her moving elegantly through the tight-packed streets, a head taller even than the men, incontrovertible physical evidence of wealth versus deprivation.

In 1920 she resigned from the council, and the following year the Marlboroughs were finally divorced. Five years later their marriage was annulled, most likely because the duke—whose new wife was another rich American, Gladys Deacon—wanted to convert to Roman Catholicism.

One of the chief grounds for annulment was coercion. Thirty years after the event, Alva Belmont testified that undue pressure had been applied upon Consuelo: “I forced my daughter to marry the Duke.” The Catholic Church, never one to hold back, denounced “the heathen practice of marriage by capture and marriage by purchase”—as if marriage had not been susceptible to this practice ever since the institution’s beginning.

An Unhappy Marriage

A quarter of a century after its annulment, by which time Sunny Marlborough was long gone—he died in 1934 at the age of 62—Consuelo wrote in a book titled The Glitter and the Gold of how spectacularly unhappy she had been as the Ninth Duchess of Marlborough, and how much she had disliked living at Blenheim.

She would not be the last highly privileged woman to write a misery memoir and look for pity. Nor was she the last heiress to exemplify the truism that money does not buy happiness. And she had a pretty fair point, of course, when she portrayed herself as the prey of both an ambitious mother and an avaricious husband, although her book—which has been described as “shockingly dishonest”—did not tell the whole story.

Consuelo signs a petition to join a suffragette group, 1914.

This was recognized from the first in a review by Lord Birkenhead, which noted Consuelo’s “flashes of engaging malice” and concluded: “It cannot be but sad for any friend of the late Duke of Marlborough to see him laid so callously upon the operating table.” (At least she waited until he was dead before taking out her scalpel.)

Both she and Sunny Marlborough were attached to other people at the time of their marriage. (The duke was in love with a young woman named Muriel Wilson, with whom he always remained friends.) It is true that he made little attempt to hide the fact. No more, however, did Consuelo. Indeed, it has been suggested that Winthrop Rutherfurd—the man whom she had wanted to marry, whom in her memoir she calls “X”—was the father of the Marlboroughs’ second son, Ivor.

In 1901 Sunny wrote a letter to a friend, the lawyer and Liberal M.P. Richard Haldane, in which he was astonishingly open about his marital situation. Obviously he felt the need to confide in somebody, and also to set out his side of the story, although the letter remained private.

It states that Rutherfurd was back on the scene just three years after the Marlborough wedding, in 1898, and that Consuelo spent two weeks with him and his sister in Paris. The inference is that Ivor was conceived on this trip; certainly this is what Sunny’s second wife believed. (Gladys Deacon confided to Hugo Vickers her belief that Ivor was the result of “two nights in Paris with an American.”)

Both Consuelo Vanderbilt and Sunny Marlborough were attached to other people at the time of their marriage.

On her return Consuelo told her husband of the relationship with Rutherfurd, who had asked her to elope with him. “I need hardly tell you that I was placed in a most painful and trying position,” wrote the duke. One might say that he had no love for his wife—only for her money, which he had started spending on Blenheim while still on his honeymoon—so what right had he to be upset? Yet upset is what he seems to have been.

At the start of 1900 Rutherfurd was back in London. “She was anxious to go and see him, and finally I allowed her to do so … I stated to her that I would not ask her to stay in my house if she desired to elope with Mr. Rutherfurd but that in consideration of her youth, her inexperience and lack of knowledge of the world I would not force her away from her home and her children. I told her that the decision must be made by her alone and pointed out to her with great care exactly what her position would be whatever course she adopted.”

The next day Consuelo had a long meeting with Rutherfurd, whose feet had clearly grown ice cold: “He declined to elope with her on the plea that he was too attached to her.” She then told her husband that she had no choice but to stay. It would be a remarkable marriage that could repair itself after such a rupture, and the Marlborough marriage had only ever been remarkable for its exterior glitz.

The French aviator Jacques Balsan, left, whom Consuelo married in 1921, at the Epsom Downs Racecourse, outside London, 1928.

“I have tried,” wrote the duke, at the end of his letter, “during the last 18 months under circumstances and situations sometimes overwhelming in the sorrow and grief that they have brought me, forcing me to bear the deepest feelings of misery, to sink entirely my own personal feelings and inclinations for these higher considerations which I felt that I was called upon to recognize. That I should offer a young woman, the mother of my children, every equitable opportunity of repairing the error of the past and that I should strive, despite the shattered home, to save her from herself from these terrible issues which her manner of life would inevitably lead her.”

Sunny went off to the Boer War, with his cousin Winston Churchill. When he returned, after six months, Consuelo informed him that she was having an affair with a cousin—the Honorable Freddie Guest, who had been living at Blenheim while the owner was away—and would like it very much if he would never enter her bedroom again.

Subsequently there were liaisons with two more Marlborough relations: the Honorable Reginald Fellowes, who later married the Singer heiress Daisy, and Charles, Viscount Castlereagh, heir to the earldom of Londonderry, whose wife, Edith, would become one of the great political hostesses. She had a lot to put up with from Charles, a truly shameless philanderer. When he wrote to her, he would generally include a letter for his current girlfriend in the envelope: “You might just send the enclosed [to whomever it might be] … That would be very sweet and dear of you.”

The relationship with Consuelo was serious—the couple ran off to Paris together—although she cannot have thought that anything would come from this quasi-elopement. Rather she seems to have been on a mission, to make her husband realize how angry she was about having had to marry him.

By this time Sunny had met the woman who would become his second wife, Gladys Deacon, with her brilliant brain, French accent, and pale-turquoise gaze. Not yet the duke’s mistress, she was enjoying the rivalrous attentions of numerous suitors. Proust and Rodin worshipped her, as did Anatole France, the art collector Bernard Berenson (and his wife), Daisy Warwick’s son Lord Brooke, and the Italian poet Gabriele D’Annunzio. So, too, did Consuelo Marlborough, who wrote to Gladys in 1904: “I have never cared for any other woman like you.”

This passion of Consuelo’s, which was physical without quite being sexual, is best described as a slight obsession, of the kind that a straight woman will sometimes feel for another. Lady Diana Cooper was similarly mesmerized by her husband’s lover Louise de Vilmorin, when Duff Cooper was British ambassador in Paris and the three formed a highly unusual ménage à trois.

For Consuelo there must also have been the simple pleasure of a female presence, a confidante with whom she had much in common: Gladys was just four years her junior, born into a wealthy East Coast family that had known scandal, albeit of a kind that frankly dwarfed Alva Vanderbilt’s divorce—her father had shot and killed her mother’s lover.

Hutton with a friend and a poodle in Palm Beach, 1940.

Equally compelling, however, was what separated them. Gladys had lived, had mixed with the kind of society represented by Madame Olenska in The Age of Innocence, while Consuelo had married in a state of absolute innocence and was now playing catch-up.

So when the Marlboroughs separated, in 1906, Gladys moved swiftly to claim the prize. She very decently burned any of her friend’s letters that made compromising reference to love affairs, before waiting 15 years for Consuelo to divorce her husband.

The duke married Gladys, then aged 40, but the delights of that long courtship (in which they had exchanged letters calling Consuelo “O.T.”: old tart) fell away almost immediately; they might have become a comfortable Prince Charles and Camilla, but instead they turned into Henry VIII and Anne Boleyn. The hanging about had gone on too long, and love turned sour in the interim.

Consuelo re-married—the wedding took place a couple of weeks after Sunny’s—to a French aviator named Jacques Balsan, who despite a roving eye had adored her for years. They lived mostly in France, where Consuelo received favored friends such as Winston Churchill, and seem to have been perfectly content. How that middle-aged bliss must have taunted Sunny Marlborough!

Marlborough and Gladys Deacon might have become a comfortable Prince Charles and Camilla, but instead they turned into Henry VIII and Anne Boleyn.

He, meanwhile, plunged headlong into a full-blown midlife crisis, which again gives the impression of being obscurely aimed at Consuelo: he took up residence in London, went dancing a great deal, and had a series of affairs (including, it was reported, a sexual tryst in a taxi). In 1933 he had Gladys evicted from Blenheim.

For Consuelo, the process of disentangling herself from the Marlborough marriage was also a series of steps toward autonomy. The fact that it affected her husband was not really the point, because the marriage had never been about the union of two people.

Its annulment made Consuelo free in a way that her divorce did not. It restored her to the self that had been forcibly buried when she was 18.

In 1957 she returned to Blenheim for the first time since the war (which she had spent in the United States, having fled France at speed in 1940). Her son was now the 10th Duke of Marlborough, and the palace presumably congenial to her at last. There was surely satisfaction in seeing what her inheritance had done for it—the replacement, and more, of what had been lost in the great sell-off of the late 19th century—the survival and triumph of something venerable and beautiful, thanks to her Vanderbilt millions.

Consuelo died in 1964, having outlived her first husband by 30 years. She was the last of her kind. Thereafter, if an heiress was unhappy in her marriage, it would be her own doing and nobody else’s.

Laura Thompson is the author of several books, including The Six: The Lives of the Mitford Sisters and Life in a Cold Climate: Nancy Mitford—The Biography. Her latest, Heiresses: The Lives of the Million Dollar Babies, will be published on February 15