Kate Middleton Apparently Had One Big Regret About Her Engagement to Prince William

• Back in October 2010, Prince William finally popped the question and proposed to Kate Middleton after years of dating.
• The engagement should have been a totally happy occasion, but Kate had one big regret about it, according to royal expert and author Katie Nicholl.
• Kate's last living grandparent, her grandfather Peter, passed away just one day before she and Will were planning to share the news with their loved ones and make a public announcement about the engagement.

Prince William famously waited years before finally popping the question and proposing to his longtime love, Kate Middleton. The engagement should have been a totally happy occasion, of course, but apparently Kate had one big regret about the milestone.

In her book Kate: The Future Queen, royal expert and author Katie Nicholl explained why the joyous event was tinged with sadness for Kate.

First, some backstory: Will popped the question at Kenya's Lake Rutundu on October 20, 2010. The couple were overjoyed, of course, but decided that they would wait a couple of weeks before making the public announcement on November 3. During that time, they didn't tell most of their friends and even family members, for fear of the new leaking early. This is where the regret comes in.

During the time between the engagement and the announcement, Kate's last living grandparent, her grandpa Peter, passed away on November 2—just one day before she was planning to share the happy news with him.

"Kate was deeply saddened not to have had the chance to tell her grandfather that she was engaged to William," Nicholl wrote, according to The Mirror. "She knew he would have been delighted for her."

Will attended the funeral with Kate and the couple delayed the announcement as a result, ultimately telling their loved ones the good news on November 16, just hours before the news was made public.