Kate Middleton curtsies to the Queen at Easter service with Prince William

The Duchess of Cambridge, Kate Middleton, curtsied to the Queen as she joined a host of other royal family members, including Prince William and Princess Beatrice at an Easter Sunday service in Windsor.

The 35-year-old beamed as she formally greeted the Queen by shifting one leg behind the other in the age-old show of respect for the 90-year-old Monarch, who arrived for the religious gathering at St George's Chapel on Saturday (15 April).

The Daily Mail report that although the mother-of-two always curtsies to Queen, this is rarely seen in public as it only happens the first time the pair meet on any given day.

Middleton wore a custom-made cream coat by her favoured designer Catherine Walker for the occasion, and was joined by her husband, Prince William, who bowed his head in honour of his grandmother's presence.

Accompanied by Prince Philip, her 95-year-old husband, the Queen wore a striking turquoise coat and hat — arriving at the chapel by car.

The Duke and Duchess' of Cambridge's children, Prince George, three, and Princess Charlotte, one, were not present at the ceremony.

But perhaps most notably of all, Prince Harry was also absent, having travelled to Toronto to stay with girlfriend Meghan Markle over the Easter period.

His father, Prince Charles, next-in-line to the throne, attended a different service with second wife Camilla at Crathie church, near Balmoral Castle in Scotland.

Extended family that did join the royals at the Windsor service included Princess Eugene, 27, who wore a beige dress and cocktail hat by London-based Goldust Millinery. Her sister Beatrice, meanwhile, opted for a high-collared dress with more intricate detailing.

Prince Edward, his wife Sophie the Countess of Wessex and children Lady Louise Windsor, James, Viscount Severn were also in attendance.

The Easter Mattins Service was officiated by the Dean of Windsor, The Right Reverend David Conner.