She was born at Windsor, but unlike her royal relatives, she had to make a living and went to work at 19. Cripplingly shy, by her own account, she nonetheless became a professional hostess, organizing over-the-top events for, as she put it, “the very rich, the very idle, the very busy and the ones who simply haven’t a clue what to do.”

Lady Elizabeth Anson, indefatigable party planner to rock stars and royals and a cousin to Queen Elizabeth II, died on Nov. 1 at a hospital in London. She was 79.

Harriet Webber-Jamieson, her longtime deputy, confirmed the death but did not specify a cause.

Lady Elizabeth could handle protocol like a general — timing to the minute, for example, the arrival of this head of state or that king to a royal wedding. She knew that the queen liked her lamb well done, and that the queen should be served the first three slices of a roast. She felt that the secret to a successful party, along with easy access to the bathroom and to the bar, was to seat the boring people together; to her mind, they would never know the difference. It was a dictum so often repeated, Mrs. Webber-Jamieson said, that guests at a Lady Elizabeth affair began to wonder if they had been seated at the boring table.

Among the many, many thousands of events Lady Elizabeth oversaw — over a half-century’s worth of glittering shindigs — were the queen’s 80th and 90th birthday parties, as well as Margaret Thatcher’s 80th. In 2000 alone, in “a dazzling triple-header” as The Times of London put it, she pulled off celebrations of Prince William’s 18th birthday (June 21), Princess Anne’s 50th (Aug. 15) and Princess Margaret’s 70th (Aug 21).

Lady Elizabeth also organized the dinner the night before the wedding of William and Kate Middleton.

But the royals were not the only clients of Party Planners Limited, Lady Elizabeth’s company, which she started in 1960. She planned the wedding of Sting and Trudie Styler in 1992, for 250 guests at Sting’s Elizabethan manor, as well as that of Sacha Baron Cohen and the actress Isla Fisher, though that apparently all went for nought when the couple ended up marrying in a secret ceremony attended by six guests in Paris, according to various reports. As was her practice, for privacy and efficiency, Lady Elizabeth assigned Ms. Fisher a code name — Sally Dangletrot — and the actress wore a succession of wigs as they toured wedding sites.

The queen’s ever-changing code name was at one point Shirley Temple, and no wigs were involved.

One of Lady Elizabeth’s first jobs was a dance party at Windsor Castle for Prince Charles, then age 15, and Princess Anne, then age 13. It was 1963, and Lady Elizabeth was stunned to learn that spinning records was a profession.

“My business started before the discothèque was invented,” she told The New York Times in 2016. “So when this man told me he was going to charge me 25 pounds to put on records for the evening, I thought, ‘Is this man absolutely crazy?’ Anybody can put on a gramophone record.”

Lady Elizabeth’s parties weren’t always so bread-and-butter. The police were once called to a bash for the Rolling Stones, in their hotel-room-trashing days, and it turned predictably raucous, ending with the guests throwing unopened bottles of Dom Pérignon out of a hotel window and into the Thames.

More recently, when she tented the back garden of an apartment building for an event, unknowingly blocking the light in a basement apartment, the enraged tenants there countered by frying fish and filling the tent with the smell of burning kippers. Lady Elizabeth reacted with typical ingenuity: She sprayed the tent with eau de toilette.

The affair proceeded as planned, and without undue odor.

In later years her team invested in a perfume gun and stockpiled gardenia scent. The gun would perfume the tablecloths and seat cushions of every party, not as a prophylactic against kipper smoke but because Lady Elizabeth liked the smell of fresh flowers, and farm-raised flowers have no odor.

A workaholic and a perfectionist, she often said that if guests weren’t comfortable — if they were cold or couldn’t find the bathroom — they would have a perfectly rotten evening, no matter how beautiful the party was or how delicious the food. For an event at the chilly Victoria and Albert Museum, at which the queen was a guest, each place setting included a hot water bottle stitched into a velvet cover, and on each chair was a pashmina wrap. Lady Elizabeth made sure that the queen had an extra hot water bottle placed under her feet.

Though her knowledge of dynastic hierarchies — political, royal or otherwise — was vast (she always knew who was on top in the complicated pecking order of ma’ams and super ma’ams, as Nancy Mitford once described obscure European royalty), Lady Elizabeth liked to say that when in doubt, one should upgrade: Drop a curtsy and smile.

Elizabeth Georgiana Anson was born on June 7, 1941, on the royal family’s Windsor Castle estate, outside London. Her father was Viscount Thomas Anson, and her mother was Anne Bowes-Lyon, whose father, John Bowes-Lyon, was the queen mother’s brother. (The queen mother was also an Elizabeth.)

Elizabeth’s parents divorced when she was 7, and her mother married Prince George of Denmark. Elizabeth was immediately sent to boarding school. She often said that she learned nothing there except good manners.

When she was 15, her father died, and her older brother, Patrick Lichfield, then just 17, inherited the family’s 17th-century estate, Shugborough Hall, in central England. Elizabeth managed it for Patrick.

“I had to grow up very quickly,” she said.

With her mother a distant presence, Lady Elizabeth planned her own debutante party, a scary and overwhelming experience that gave her the inspiration for her business.

In 1972 she married Geoffrey Shakerley, a baronet, at Westminster Abbey. Princess Anne was a bridesmaid. The couple divorced in 2009.

Lady Elizabeth is survived by her daughter, Fiona Burrows; two stepsons, Joth and Nicholas Shakerley; and four grandchildren.

Lady Elizabeth was not immune to personal and financial setbacks. In the early 1990s, an investment in Lloyd’s of London, the insurance market, vanished when the company’s losses left her and thousands of wealthy investors liable in the financial crisis.

In 1993, when Ivana Trump, newly divorced from Donald J. Trump, hired Lady Elizabeth to organize a 50th-birthday party for Ms. Trump’s fiancé at the time, Riccardo Mazzucchelli, and then doubled the guest list, Ms. Trump refused to pay the difference. The two spent years in court as Lady Elizabeth fought to recoup the amount, about $9,000. She lost.

In 2001, she was robbed in her house on Ladbroke Grove in West London by masked invaders, who attacked her while she was watching television and stole her jewelry.

She played the lottery every week. She never won.

Despite the crises, Lady Elizabeth remained the embodiment of the wartime slogan “Keep calm and carry on,” her favorite phrase, said Mrs. Webber-Jamieson, to whom she left her business.

“She was the bravest person I know,” she added. Though Lady Elizabeth suffered from chronic fatigue syndrome and a respiratory illness, Mrs. Webber-Jamieson said, “once the hair and makeup was on, it was showtime.”