Prince Harry reveals Prince William's nickname for Kate Middleton.

It seems that Prince William has a special nickname for Kate Middleton and it all started when they first started seeing each other. Prince Harry was the one who shared the secret and chose to do so during his best man's speech for the couple's wedding back in 2011. He explained that he first knew it was serious between his brother and Kate when he heard William call her 'Babykins'. Yes, really. Apparently, this was during a phone call with Harry describing his older brother as "cooing" to his girlfriend. This tidbit of royal gossip was revealed by Katie Nicholl in her biography Harry: Life, Loss and Love. According to Katie, Harry even imitated the voice William used to speak to his other half, embarrassing his brother on his wedding day as is a tradition for many best men. The Express reports that Harry spoke about how previously William "didn't have a romantic bone in his body" and this was a major change. It seems that Chelsea Davy, Harry's former girlfriend was the one to help Harry with this best speech and she also recommended that he remove a line about Kate's "killer legs" as this could embarrass the Duchess of Cambridge on one of the biggest days of her life. Good point, Chelsea.