Prince William has unexpectedly pulled out of a memorial service for the late King Constantine of Greece citing a “personal matter.”

Kensington Palace made the surprise announcement on Tuesday morning, prompting concerns for Kate Middleton’s health. Princess Kate is recuperating following major abdominal surgery at the family home in Windsor and is not expected to return to royal duties until after Easter.

Palace aides have said that the princess “continues to be doing well,” but the suddenness of William pulling out of Tuesday's memorial service has prompted widespread concern.

Prince William had been due to attend the service in Windsor as he is a godson of the late king and personally called the family to let them know that he would be unable to attend.

Kensington Palace would not elaborate any further other than to explain that William was unable to attend because of a “personal matter.” With Kate still recovering after undergoing abdominal surgery in January and King Charles undergoing cancer treatment, the announcement has come as a surprise. Willliam was due to give a reading at the memorial service but Crown Prince Pavlos stepped into his place.

William has resumed royal duties after taking two weeks off work during Kate’s hospitalization in January. He was off work recently for half term, but with the children all back at school, William has been busy attending events including the BAFTA awards.

On Tuesday, it was once again Queen Camilla who led the charge in representing the royal family at the memorial service at St George’s Chapel in Windsor Castle, just a stone’s throw from the Waleses’ residence.

Charles, who is undergoing cancer treatment as an outpatient, was seen in Windsor on Tuesday morning but aides confirmed he would not be attending the service. Palace sources have also said that William’s absence is not due to the Charles’ health, casting a mystery as to why he was unable to attend.

In Charles’ absence it has largely fallen to Camilla to carry on with royal engagements on the king's behalf. At the memorial, Camilla, dressed in an elegant pinstripe dress, was well supported by other family members including Princess Anne and her daughter Zara Tindall and husband Mike Tindall, Prince Andrew and his ex-wife Sarah Ferguson, Princess Beatrice and her husband Edoardo Mapelli Mozzi, Prince and Princess Michael of Kent and Prince Richard, Duke of Gloucester and Birgitte, Duchess of Gloucester.