Diana, Princess of Wales during her visit to Bosnia in August 1997. Picture: AP

It was a question that caught her off guard. Just hours after announcing their engagement in 1981, the late Princess Diana was asked by a reporter "are you in love?"

Now shocking information has come to light on how Diana admitted she only met Prince Charles 13 times before they wed. According to The Express, Diana revealed during an interview with her voice coach during the 1990s that she was left "traumatised" after the interview announcing their engagement.

“I thought, what a thick question," she said.

“So I said, ‘Yes, of course, we are,’ and Charles turned round and said, ‘Whatever love means.’

“And that threw me completely.

“I thought, what a strange answer."

WATCH: Charles and Diana's engagement interview

In in his book ‘Diana: Her True Story’, author Andrew Morton claimed that Diana had raised the question as to whether the British royal family would be relevant in a federal Europe.

A friend said: “She feels that it is a crumbling institution and believes that the family won’t know what has hit is in a few years’ time unless it changes too’.”

The couple separated in 1996 after 15 years of marriage.

On the day they separated, one royal expert spoke of the question Diana uttered to Charles.

Writing in her book, ‘The Queen and Di: The Untold Story’, Ingrid Seward touched on a specific moment the pair met for the first time following their separation.

The two met in Kensington Palace in the first-floor drawing room Diana called the salon of her apartment.

Walking into the room, Diana allegedly asked Charles, “Why did this have to happen?”. 

Diana died the next year in a horrific car crash in Paris, while Charles went on to marry Camilla Parker Bowles.