For as long as she's been in the public eye, the Duchess of Cambridge has been primarily referred to as Kate Middleton. There have been a few particular formal occasions when she'd been called her full name of Catherine, but she is typically just called Kate within the media.
However, there was reportedly once a time when Middleton did wish for start the process of shifting away from Kate and on to Catherine. At least, that's what she said in an email to some of her friends, according to Express.
Back in 2008, rumors began to circulate that Prince William would likely be proposing to Middleton in the near future. There was a lot of speculation about what name Middleton would go by if she did in fact become a royal. After all, Catherine does seem far more formal and duchess-like than Kate. Many believed that those close to Kate, even her own friends, would have to become used to calling her Catherine.
Around that time, Middleton reportedly wrote an email to some of her friends in which she informed them that she'd like them to call her by her full name: Catherine. The future royal's request was said to be offered in a gentle and joking tone, but some might not have sensed that.
At the time, Express columnist Adam Helliker informed the public that Middleton was slowly making changes in her life as she began to prepare to become a member of the royal family.
"With Prince William's engagement now a surefire certainty (even Ladbrokes has stopped taking bets on whether it will happen after a flurry of well-placed wagers) there are intriguing signs that Kate Middleton is preparing for her future role. It looks like she's taking it very seriously indeed too. I hear that in the past few weeks the former accessories buyer has quietly informed friends that she would like to drop the informal 'Kate' and in future wishes to be known by her full name: Catherine."Even though Middleton probably didn't want to offend anyone with her email, some of her friends were reportedly taken aback by the request. It appeared that by changing her title, Middleton was beginning to take herself more seriously and was becoming even further aware of her position of authority. Today, Middleton is referred predominately as the Duchess of Cambridge within statements from Kensington Palace and doesn't seem to bothered by what people call her.