SANDRINGHAM, England (Reuters) - Britain’s Prince Philip, Queen Elizabeth’s husband, missed a traditional Christmas Day church service on Tuesday, though a royal source said that the 97-year old was in good health and just wanted to spend the day in private.

Philip, the Duke of Edinburgh, married Elizabeth in 1947 and has been by his wife’s side throughout her reign, the longest in British history.

“The duke is in perfectly good health, he is just spending the day privately,” the royal source said.

Former naval officer Philip, who had successful hip replacement surgery earlier this year, retired from public life last year, quipping at the time that he was no longer able to “stand up much”.

Senior members of the royal family traditionally attend a Christmas service at the St Mary Magdalene church in Sandringham, eastern England.

Elizabeth attended, as did Charles, Prince of Wales, heir to the throne. Charles’ wife, Camilla, did not attend, according to a Reuters photographer at the church.

Charles’ sons, Princes William and Harry, also went to the service with their wives, Kate and Meghan.

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The U.S. born actress, who is pregnant, exchanged a smile with Kate as they walked to church.

Elizabeth will say in her Christmas message that the traditions of peace and goodwill need to be heeded as much as ever, and people should respect each other even when they harbor the most deeply held differences.

According to excerpts released by Buckingham Palace, the 92-year-old monarch will also speak of family and friendship following a year in which her grandson Harry married Meghan at a dazzling ceremony.

The queen has avoided commenting in public on contentious issues, and the excerpts make no mention of the visit in July by U.S. President Donald Trump or the turmoil over Britain’s departure from the European Union.

Speaking about the birth of Jesus, she will say: “I believe his message of peace on earth and goodwill to all is never out of date. It can be heeded by everyone; it’s needed as much as ever.”

“Even with the most deeply held differences, treating the other person with respect and as a fellow human being is always a good step towards greater understanding.”