In the third episode of the new season of “The Crown,” Lady Diana Spencer moves into Buckingham Palace a few weeks before her wedding to Prince Charles.

She is all alone.

The prince has just left town on a foreign junket, leaving his future bride but not his true love — everyone, including Diana, knows it’s Camilla Parker Bowles — for royal instructional courses, including curtsying.

One evening, Diana, played by Emma Corrin, strolls through the quiet palace in her pajamas and robe. Soon she appears in the kitchen, cracking open a refrigerator filled with enough desserts to satiate the Royal Navy.

Diana takes a spoonful of chocolate mousse, then moves on to a pastry, then pudding. She savors every bite, exhaling with pleasure. Here is the future princess basking in the glory of a darkened palace with a fully stocked fridge that her old flatmates would no doubt squeal in joy over.

But the next scene tells a different story, introducing into the show — a fictional drama inspired by true events — the disease that Diana struggled with for years. Her head is over the toilet. She is vomiting up the desserts she just ate. The sounds are disturbing.

Lady Diana has bulimia.

The arc of Diana’s transformation from house cleaner to princess to a jilted, damaged soul plays out over the course of the show’s fourth season. Many of her scenes are painful and true, including a bizarre lunch she had with Camilla before the wedding. But Diana’s struggles with bulimia are the most jarring.

She spoke openly about the disease before her death in 1997.

“You inflict it upon yourself because your self-esteem is at a low ebb, and you don’t think you’re worthy or valuable,” she told the BBC’s Martin Bashir in 1995. “You fill your stomach up four or five times a day — some do it more — and it gives you a feeling of comfort. It’s like having a pair of arms around you, but it’s … temporary. Then you’re disgusted at the bloatedness of your stomach, and then you bring it all up again.”

The bulimia began early in her troubled relationship with Charles, she told biographer Andrew Morton.

“My husband put his hand on my waistline and said: ‘Oh, a bit chubby here, aren’t we?’ and that triggered off something in me — and the Camilla thing, I was desperate, desperate,” she said.

On her honeymoon, Diana was vomiting three or four times a day.

“By then, the bulimia was appalling, absolutely appalling,” she told Morton. “Anything I could find I would gobble up and be sick two minutes later.”

There were many strains on the marriage. The prince’s continued love for Camilla. The constant presence of the paparazzi. The rigid monarchy and a distant mother-in-law who was also the queen of England.

But inside the family’s many castles, the royals blamed the couple’s troubles on Diana’s eating disorder.

In a conversation with the queen, Diana told Morton, “she indicated to me that the reason why our marriage had gone downhill was because Prince Charles was having such a difficult time with my bulimia.”

This startled her.

“She hung her coat on the hook, so to speak,” Diana said. “And it made me realize that they all saw that as the cause of the marriage problems and not one of the symptoms.”

The princess told Bashir in the BBC interview that some members of the royal family thought she was wasting food.

This startled Bashir.

“What was said?” he asked.

“Well, it was just, ‘I suppose you’re going to waste that food later on?’ And that was pressure in itself,” Diana said. “And of course I would, because it was my release valve.”

Diana’s eating disorder continues throughout the fourth season of “The Crown,” including during and after the surreal lunch she shared with Camilla. (Though the lunch took place both off screen and on, it’s not known whether she actually vomited after it.)

Diana told Bashir that the disease continued for several years until she got professional help. And she never shied away from talking about it — especially as a symptom, not the cause, of her troubled marriage.

“Anything good I ever did,” Diana told Bashir, “nobody ever said a thing, never said, ‘Well done’ or ‘Was it okay?’ But if I tripped up, which invariably I did, because I was new at the game, a ton of bricks came down on me.”

“How did you cope with that?” Bashir asked.

“Well, obviously, there were lots of tears,” she said, “and one could dive into the bulimia, into escape.”

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