The Prince of Wales has missed a memorial service for his godfather the late King Constantine of Greece because of a personal matter.

Kensington Palace would not elaborate further but said the Princess of Wales, who is recovering from abdominal surgery, continues to be doing well.

Queen Camilla led the royal family at the St George’s Chapel service, attended by a large number of Constantine’s family and foreign royalty, as the King is continuing to receive treatment for cancer.

Among those in the congregation were the disgraced Duke of York who with ex-wife Sarah, Duchess of York led the main contingent of British royals as they walked downhill from Windsor Castle to the church.

Andrew smiled as he strode ahead of Sarah followed by their daughter Princess Beatrice with husband Edoardo Mapelli Mozzi, the Princess Royal and her husband Vice Admiral Sir Tim Laurence, Zara and Mike Tindall and the King’s cousin Lady Sarah Chatto.

Constantine II’s widow Queen Anne-Marie was joined by their children, Crown Prince Pavlos, Princess Alexia, Prince Nikolaos, Princess Theodora, Prince Philippos, and a number of their grandchildren.

Former prime minister Sir John Major was also invited by the Greek royal household to the service as was ex-Formula One racing driver Sir Jackie Stewart and King Felipe VI and Queen Letizia of Spain.

William called the Greek royal family to let them know he was unable to attend, and Crown Prince Pavlos stood in for the British heir to the throne who was due to give a Bible reading.

The King stayed overnight at Windsor Castle but did not meet any of the guests ahead of the service and had left before a reception was held afterwards at the royal residence.

Charles was close to his second cousin Constantine, who was a first cousin once removed and sailing partner of the late Duke of Edinburgh.

Constantine died at the age of 82 in January last year, decades after being toppled from the throne in a military coup.

Charles was later spotted arriving in the capital where he is expected to receive further cancer treatment as an outpatient.

He was photographed arriving at Clarence House and since his diagnosis has postponed all public-facing duties, but is continuing with behind-the-scenes work on his red boxes of state papers and his weekly meetings with the Prime Minister.

Kate left hospital on January 29 and returned to her Adelaide Cottage home close to Windsor Castle but is not expected to return to official duties until after Easter.

Constantine was also godfather to Prince and Princess of Michael of Kent’s daughter Lady Gabriella Kingston.

She did not attend, although her parents did, and it later emerged Lady Gabriella’s husband Thomas Kingston died suddenly on Sunday.