Along with The King and Queen Camilla, Prince William and Princess Kate, who share a close bond with the Edinburghs, are said to be joining the festivities. The Princess of Wales and Duchess of Edinburgh are said to have a particularly strong relationship, with Kate viewing Sophie as a sort of "royal sister."

It’s a milestone birthday for Duchess Sophie, who officially rang in the special day on January 20 with a little more pomp and circumstance than usual, courtesy of an official new portrait and plans for a major birthday celebration at their Berkshire home Bagshot Park.

London-based fashion photographer Christina Ebenezer created Duchess Sophie's beautiful new portrait. Sharing the photographs on Instagram, the Royal Family's official account revealed, " The Duchess of Edinburgh was interested in Ebenezer's creative style of photography and wanted to support a rising female photographer."

Congratulations are in order as Duchess Sophie gears up to celebrate her 60th birthday on Monday 20 January. In a slight deviation from tradition, the Royal Family has already marked the special day, taking to Instagram today to share a new photos showing the Duchess looking relaxed and happy ahead of the celebrations.

I love how she is not afraid to try new things and she makes beautiful choices,” designer Suzannah Crabb of royal favorite Suzannah London tells PEOPLE