The Duchess of Cambridge has marked her milestone 40th birthday by releasing photographic portraits showing the sophisticated glamour of the future queen.

Kate has been pictured in relaxed poses, wearing different Alexander McQueen dresses and with her hair flowing.

Celebrated fashion photographer Paolo Roversi, famed for working with industry stars like Naomi Campbell and Kate Moss, described photographing the duchess as “a moment of pure joy” and said with her “positive energy” she can “bring hope to the whole world”.

When is Kate Middleton 40?

The duchess will celebrate her 40th birthday on Sunday (January 9) and the event is likely to be a private family affair marked at the Cambridges' home in Norfolk.

The birthday heralds the start of an important decade for the monarchy and the future queen, who will be at William’s side as events progress, watching her young family grow up and pursuing her own charitable interests.

Roversi said: “Taking the portrait of Her Royal Highness the Duchess of Cambridge was a true honour for me and a moment of pure joy.

“I was moved by her warmth and friendly welcome and enchanted by her shining eyes that reflected the loveliness of her soul and her smile showing the generosity of her heart.

“It was a profound and rich experience for me, an unforgettable moment. I have met a wonderful person, a person who, with her positive energy, can bring hope to the whole world.”

Duchess of Cambridge birthday photos

In one image Kate wears a striking red McQueen dress, earrings loaned by the Queen and beams at the camera as she appears to have her hands casually in the gown’s pockets.

Roversi is known for his adventurous film and printing techniques and the remaining images have been produced in monochrome that give them an ethereal quality.

Swanage and Wareham Voice: With her engagement ring prominently on display, Kate Middleton is shown in profile. Picture: PA/Paolo RoversiWith her engagement ring prominently on display, Kate Middleton is shown in profile. Picture: PA/Paolo Roversi

In one, a head and shoulders image, the duchess smiles broadly and in the other, with her engagement ring prominently on display, Kate is shown in profile and expressionless looking left.

She wears earrings that belonged to Diana, Princess of Wales, in both of these photographs.

Kate Middleton's public life

Ahead of her birthday the duchess was praised for her “vision and commitment” in establishing her Royal Foundation Centre for Early Childhood to support the development of children.

Kate’s work championing research into a child’s formative years is the cornerstone of her public life and has been highlighted by a senior figure from one of the country’s leading mental health charities for children and young people.

Michael Samuel, chairman of trustees at the Anna Freud National Centre for Children and Families, said Kate had shown “passion and compassion” in her role as the organisation’s patron.