According to reports, the intimate celebration was held in a private quarters at one of their properties near the couple’s Kensington Palace home.
A source said: “Yes, it’s a milestone birthday, but it’s been a year of milestones for Kate and she’s happy to keep things low key.”
“She will be celebrating it but it will just be with a few people and it won’t be anything fancy.
“Of course she wants to raise a glass to an incredible year and to this new decade of her life but she doesn’t feel the need to go wild.”
In response to all the good wishes that have been tweeted, Clarence House followed-up with a tweet of their own, saying, “Thank you for all your #happybirthday messages to The Duchess of Cambridge today. They were all very much appreciated.”