Prince William is said to have made a heartfelt promise to commit to the Princess of Wales long before they got married.
It is believed that in the earlier days of their relationship, William was not ready to tie the knot with his now-wife, but did not want to lose her.
Royal author Katie Nicholl describes an alleged private moment between the pair that might have sealed their fates, with William making a promise that a lifelong commitment to Kate would come, in her book, The Making of a Royal Romance.
The pair suffered a brief breakup in 2007, which William later discussed in their 2010 engagement interview. He shared at the time, "We were both very young. We were finding ourselves. It was very much trying to find our own way, and we were growing up."
Following the split, William and Catherine went on an under-the-radar holiday to Desroches, an island in the Seychelles. It was here that William vowed that Kate would indeed be queen one day.
In her book, Katie writes, "William, who had inherited something of his father's fear of commitment, knew he would lose Kate if he could not give her some form of guarantee.
"They didn’t agree to get married there and then; what they made was a pact. William told Kate she was the one, but he was not ready to get married. He promised her his commitment and said he would not let her down, and in turn, she agreed to wait for him."
Proving it was well worth the wait, William would go on to propose to Catherine three years later during a trip to Kenya, proposing to her with the iconic sapphire engagement ring that had previously belonged to his mother, Princess Diana.
Despite William’s promise during that fated Seychelles trip, the Princess of Wales revealed in their 2010 engagement interview that the proposal was a "total shock" when it came.
It was during this interview that the couple shared details of how their romance first began to blossom at St Andrews University, with Prince William saying, "We just spent more time with each other had a good giggle, had lots of fun and realised we shared the same interests and had a really good time.
"She's got a really naughty sense of humour, which kind of helps me because I've got a really dry sense of humour, so it was good fun, we had a really good laugh and things happened."
