Prince Charles and Duchess Camilla (72) first appeared in public as a couple in 1999, but it took quite some time for them to get engaged. In fact, the heir apparent to the British throne waited six years until he asked Camilla to marry him.

In her book "The Firm: The Troubled Life of the House of Windsor" the royal biographer Penny Junor names the reasons for the long wait. "A not insignificant part of the reason why they had waited until 2005 to announce their engagement was a sensitivity towards the boys."

Prince Charles and Camilla waited for William and Harry's sake

"They didn’t want to foist a stepmother on William and Harry before they had fully grown up," the author continued. It was not easy for the two sons to accept their father's new relationship.

"Although they have been genuinely pleased to see him so happy, and genuinely like Camilla – and her children – the issue is complicated."

"The notion that their mother was a sacrificial extra in a long-standing love story between Charles and Camilla  – a line most of the newspapers ran after their engagement – is hurtful. They loved their mother and are fiercely loyal to her memory – and know that Camilla was the cause of her terrifying unhappiness."

How close Diana's relationship was with her two sons, becomes apparent when looking at the pictures from Princess Diana's private photo album.

Camilla's father spoke to Prince Charles

In another biography, "The Duchess: The Untold Story", Penny Junor describes how the engagement then came to pass. Camilla's father Bruce Shand is said to have persuaded Charles - out of concern for his daughter.

Apparently, Bruce "was worried about how vulnerable he [Charles] had made Camilla by allowing her to live in limbo." And Charles made sure that she didn't have to wait any longer - the royal couple has now been married since 2005 already.