Their wedding was watched by more than 300 million people around the world and over 26 million in Britain alone.
Before the big occasion, Queen Elizabeth II hosted a private meeting with Kate to prepare her for the day.
Now, details of the conversation have been aired on Amazon Prime’s “Kate Middleton: Working Class to Windsor”.
In it, the narrator says: “Kate met with Queen Elizabeth shortly before the wedding.
“It was confirmed that her title would be Catherine: Her Royal Highness, the Duchess of Cambridge.”
It was not the only preparation she went through before her wedding day, though.
Freelance journalist Ashley Pearson later revealed that Kate was actually given lessons on how to be a royal wife.
Kate Middleton: Working Class to Windsor is available to watch on Amazon Prime now.