Prince Andrew, the Duke of York, making a rare public appearance, led a group of his own family members, including his ex-wife Sarah, Duchess of York, and Princess Beatrice. Zara and Mike Tindall arrived at the chapel by coach.

Andrew, who attended in a personal capacity on the invitation of the Greek royal family, was warmly greeted on arrival by the Right Reverend Christopher Cocksworth, the Dean of Windsor, and sat in the front row.

Anne, the Princess Royal, 73, who has just returned from Namibia, where she attended a memorial for late president Hage Geingob on behalf of the King, was also present with her husband, Vice Admiral Sir Tim Laurence.

They were joined by the Duke and Duchess of Gloucester, Princess Alexandra, 87, who was in a wheelchair, and her daughter, Marina Ogilvy, and the Duke of Kent, 88.

Other guests at the sombre, hour-long service included Sir Jackie Stewart, the former Formula One world champion, and Penny Knatchbull, Countess Mountbatten of Burma, both close friends of the Royal family.

The Queen, 76, smiled as she arrived at the entrance to the chapel shortly before 11am in a navy wide-brimmed hat, a matching pinstripe blazer and skirt.

As she took her seat inside, she had a brief chat with Princess Anne, who was sitting next to her.

The Dean, who gave the bidding, said King Constantine, who was forced into exile following a military coup, had “lived through times of great change and challenge”.

He added: “We give thanks for his unwavering commitment to the good of his people, his steadfast love of his wife and family, his ability to face the future with hope and faith even in the face of adversity.”

The first reading, Ithaka by C P Cavafy, was read by King Constantine’s children – Princess Theodora, Prince Nikolaos, Princess Alexía and Prince Philippos.

The bible reading, Revelation 21. 1–7 that Prince William was due to give was instead given by the late king’s elder son, Crown Prince Pavlos.

The service ended with the Russian Orthodox chant known as the Kontakion of the Departed, which was sung at the Duke of Edinburgh’s funeral in April 2021.

The Queen later hosted a private reception for guests, including Queen Anne-Marie, the former queen of the Hellenes, at Windsor Castle, just a stone’s throw from Adelaide Cottage, home to the Prince and Princess of Wales and their children.

Catherine was admitted to the private London Clinic for abdominal surgery on January 17. She was discharged almost two weeks later and is now recuperating at home in Windsor. She is not expected to return to work until after Easter.

William immediately cancelled all engagements in his diary to look after his wife and their three children. He has carried out only a handful of public duties since she was discharged.

The King was admitted to the London Clinic for treatment for an enlarged prostate just days after his daughter-in-law underwent surgery.

During the procedure, further tests were carried out, and it emerged days later that he had an undisclosed form of cancer, prompting him to cancel all public-facing duties as he underwent treatment.

Loading

Constantine, Greece’s final King, who reigned from 1964 until 1973, died on January 10 last year, aged 82.

Constantine was godfather to William and Lady Gabriella Windsor, the daughter of Prince and Princess Michael of Kent.

He was a first cousin once removed and sailing partner of the late Prince Philip and enjoyed a close friendship with the King.

It was at his 60th birthday party at Highgrove in 2000 that Prince Charles finally introduced Camilla Parker Bowles to his mother, Elizabeth II.

The young Constantine, who had won Olympic gold in sailing, was initially hugely popular.

But he had squandered much of that support with his active involvement in the machinations that brought down the popularly elected Centre Union government of then-prime minister George Papandreou.

The episode, still widely known in Greece as the “apostasy” or defection from the ruling party of several politicians, destabilised the constitutional order and led to a military coup in 1967.

Constantine eventually clashed with the military rulers and was forced into exile.

The dictatorship abolished the monarchy in 1973, and a referendum after democracy was restored in 1974 dashed any hopes Constantine had of reigning again.

He lived in exile for many years in Hampstead Garden Suburb in north London before returning to his home country in 2013.

The Telegraph, London