'The Crown': How Prince Charles Met Diana—and the Very Formal Name She Had to Call Him

Princess Diana first met Prince Charles while he was still dating her sister—and had to call him "Sir" until they were engaged.

Season four of The Crown sheds light on the ill-fated relationship between the Prince and Princess of Wales.

The first episode depicts a 16-year-old Princess Diana dressed as a woodland nymph hiding behind a plant pot to catch a glimpse of Chares at her family estate, Althorp.

However, the full story of their extraordinary royal romance was first exposed in the 1992 unauthorised biography Diana: Her True Story, by Andrew Morton, which she secretly co-operated with.

The author describes the meeting in very different terms to The Crown, and particularly Diana's outfit, though her age at the time is correct.

Morton wrote: "That historic meeting in November 1977 was hardly auspicious.

"Diana, on weekend leave from West heath School, was introuduced to the prince in the middle of a ploughed field near Nobottle Wood on the Althorp estate during a day's shooting."

He added: "Diana cut a nondescript figure in her checked shirt, her sister's anorak, cords and wellington boots."

The author details how Diana's sister Sarah was dating Charles and showed some signs of jealousy.

The future princess told Morton she thought: "God, what a sad man."

The book quotes Diana saying: "I kept out of the way. I remember being a fat, podgy, no make-up, unsmart lady but I made a lot of noise and he liked that and he came up to me after dinner and we had a big dance."

Morton writes: "By any standards it was an unusual romance. It was not until Lady Diana Spencer was formally engaged to His Royal Highness the Prince of Wales that she was given permission to call him 'Charles.'

"Until then she had demurely addressed him as 'Sir.' He called her Diana. In Prince Charles' circle that was considered the norm."

A year later, aged 17, she was invited, with her sister, to Prince Charles' 30th birthday party.

Then, in July 1980, they were together again at the house of mutual friends Commander Robert De Pass and his wife Philippa, in Petworth, West Sussex.

The book quotes Diana saying she told Charles: "You looked so sad when you walked up the aisle at Lord Mountbatten's funeral. It was the most tragic thing I've ever seen.

"My heart bled for you when I watched. I thought: 'It's wrong, you're lonely, you should be with somebody to look after you.'"

Morton describes how her comments "struck a chord" with Charles and she was soon "overwhelmed by his enthusiastic attentions."

Diana herself went further in tapes she recorded years later with her speech therapist Peter Settelen, which were broadcast by NBC in 2004.

She told the former actor: "Whereupon he leapt upon (me), he started kissing me and everything and I thought, 'Ahh, you know, this is not what people do,' and he was all over me for the rest of the evening, followed me around, everything.

"A puppy. And, yeah, I was flattered, but it was very puzzling. He wasn't consistent with his courting abilities.

"He'd ring me up every day for a week and then he wouldn't speak to me for three weeks, very odd.

"And I'd accepted that and I thought fine, he knows where I am if he wants me. And then the thrill when he used to ring up was so immense and intense, drive the other three girls in my flat crazy. But no, it was all, it was odd."

They continued dating and their engagement was announced in February 1981 after, Diana told Settelen, they had met just 13 times.

However, by then Diana already suspected something was wrong in a relationship that was defined by Charles' affair with Camilla, now the Duchess of Cornwall.

Diana told Settelen: "I was brought up in the sense that, you know, when you got engaged to someone, you loved them.

"The most extraordinary thing is we had this ghastly interview the day we announced our engagement and this ridiculous ITN man said, 'Are you in love?'

"I thought what a thick question so I said, 'Yes, of course we are,' in the sort of Sloane Ranger I was, and Charles turned round and said, 'Whatever "in love" means.'

"That threw me completely. I thought what a strange question and answer. God. Absolutely traumatised me.

"No, I didn't dare (ask him about it). Must have been (frightened), yeah. We met 13 times before we got married."

As depicted in season four of The Crown, Diana married Charles on July 29, 1981, at St. Paul's Cathedral, in London.