Kate Middleton describes her 40th birthday portraits as 'special' as she thanks fans for messages

Kate Middleton is celebrating her 40th birthday today. (Getty Images)
Kate Middleton is celebrating her 40th birthday today. (Getty Images)

Kate Middleton took time away from celebrating her 40th birthday on Sunday to thanks fans for their messages.

In an Instagram post, the Duchess of Cambridge also described three new portraits, released to mark her milestone occasion, as "special".

Captioning an image of one of the shots, she wrote: "Thank you for all of your very kind birthday wishes, and to Paolo and the National Portrait Gallery for these three special portraits."

The images, showing the mother-of-three posing in an array of Alexander McQueen dresses, were taken by photographer Paolo Roversi and will be displayed by the National Portrait Gallery.

Kate's latest post has received more than 691,000 'likes', with social media users commenting that the shot was "stunning" and "beautiful".

In another of the portraits, also shared to Instagram earlier today, Prince William's wife paid tribute to Princess Diana.

She wore a pair of diamond and pearl drop earrings as well as her blue sapphire engagement ring that both previously belonged to her late mother-in-law.

It has been revealed that the royal birthday girl sat for the photos at Kew Gardens in November.

Members of the public will eventually be able to see the images on display in locations of significance to the duchess.

The caption to the third Instagram post released today read: "The three new portraits which have been released to mark the occasion will be shown in the community in three meaningful places: Berkshire, St Andrews, and Anglesey."

Berkshire is where the duchess grew up and where her parents still live, while St Andrews is where she met her husband, and the couple moved to Anglesey after their wedding in 2011.

However, it has not just been members of the public who have been sending their well-wishes, but also senior members of the royal family.

The Queen enlisted a balloon emoji when she sent the duchess a birthday message on Instagram earlier today.

She also shared several throwback photos of the pair carrying out official engagements together.

Similarly, Prince Charles and Camilla, Duchess of Cornwall used a cake emoji and some more throwback pictures in an Instagram post of their own.

It is unclear how the duchess is celebrating, but she is likely to be spending the day with her children Prince George, Princess Charlotte and Prince Louis.

Watch: Everything you need to know about Kate and William's children