"Can I let you in on a secret?" she said. "I was asked to do Kate Middleton for her engagement pictures with Mario Testino, but couldn't because I was already booked.
"Now I would give up my right arm to make her up. Tell her to call me – at any time."
The make-up maven has worked with handfuls of stars including Sienna Miller, Penelope Cruz, Eva Mendes and Cara Delevingne.
She was also responsible for making sure Kate Moss looked her best on her wedding day. "I love making women feel good about themselves – isn't that what make-up is all about?" she said.
"Give a woman the right make-up and she can conquer the world."
Charlotte recently launched an eponymous beauty range. On Monday 2 September, the full collection of skincare and make-up will launch at Selfridges Oxford Street along with celebrity inspiration for each look and step-by-step guides to recreating them yourselves.
"Think of it as having my make-up kit – and my tricks and tips – at your fingertips," Charlotte told HELLO!. "I honestly want my make-up to change women's lives."
For the full interview with Charlotte, pick up a copy of HELLO! Magazine – issue 1292 – out now.