Princess Diana was allegedly chastised by Prince Charles for wearing a black gown to their first official engagement as a betrothed couple.

Before appearing at a charity performance at Goldsmiths Hall in London on March 9, 1981, Charles and Diana allegedly fought about the outfit.

According to author Andrew Morton, who included it in his book Diana: Her True Story in 1992, Diana recounted the dispute with Charles in a taped interview.

“I remember walking into my husband-to-be’s study, and him saying: ‘You’re not going in that dress, are you?’ I replied: ‘Yes, I am’. And he said: ‘It’s black! But only people in mourning wear black!'” Diana reflected.

Diana said on the recordings that she was unaware of the royal clothing rules and just wanted to look like ordinary teenagers.

“I thought it was OK because girls my age wore this dress, Princess Diana revealed in the secret tapes.

“It was a horrendous occasion. I didn’t know whether to go out of the door first,” she later told Mr Morton.

“I didn’t know whether your handbag should be left in your left hand or your right hand.

“I was terrified really – at the time everything was all over the place.”

Many stylistic restrictions and conventions apply to members of the British royal family, including avoiding wearing black, which is usually reserved for funerals.

Diana broke a trend with her usage of black gowns, according to Alexandra Messervy, CEO of The English Manner etiquette training company.

“Generally it is thought that black is not usually worn unless in mourning, although Diana Princess of Wales did occasionally wear it for evening functions,” says the source.

The black satin gown that drew instant notice was created by British designers Elizabeth and David Emanuel, who previously created Diana’s eye-catching wedding gown in 1981.

Later, on the same evening that a program aired on national television in which the Prince of Wales confessed he had been unfaithful to her, the Princess wore a black off-the-shoulder Christina Stambolian gown.

PRINCESS DIANA ARCHIVE

For a variety of reasons, the dress violated royal regulations, but its color may have been a reference to the early encounter, indicating that she was no longer dressed for her husband’s or the royal family’s approval.

Diana was just 19 when she married Charles, who was 32 at the time. She has been instructed to dress in the same manner as other members of the royal family.