Prince Charles once got angry with Princess Diana for wearing black dress

Prince Charles once reportedly scolded Princess Diana for donning a black dress to their first royal engagement as a betrothed couple.

Charles and Diana reportedly argued over the dress ahead of their appearance in a fundraising concert at Goldsmiths Hall, London on March 9, 1981.

The royals abide by many style rules and protocols. They reportedly sport black clothing during periods of mourning.

Prince Harry's mother revealed the details about the incident during a secretly recorded interviews in 1991 for her biography "Diana: Her True Story" by Andrew Morton, which was revised in 2017 and titled "Diana: Her True Story — In Her Own Words."

"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.

"I thought it was OK because girls my age wore this dress. I hadn't appreciated," Princess shared the details in the secret tapes.

The Princess reportedly wore a black off-the-shoulder Christina Stambolian gown on the same evening that a documentary aired on national television in which Prince of Wales admitted he had been unfaithful to her.

Diana was only 19 when she got engaged to Charles, 32. She was told to follow the same fashion trends as the other royals do.