Queen Elizabeth and Prince Philip will miss the royal christening of their great-grandson Prince Louis

Queen Elizabeth and Prince Philip will miss the royal christening of their great-grandson Prince Louis, the palace surprised royal watchers by announcing early on Monday.

The decision that she would not be attending the event was “mutually agreed” between the 92-year-old monarch, Prince William and Kate Middleton “some time ago,” a palace source tells PEOPLE.

The Queen’s absence is likely due to her busy schedule. She just capped off a heavy work week and she has another one in the week ahead. Amid other commitments, she is marking the 100th birthday of the Royal Air Force at a Westminster Abbey service in London on Tuesday and a flypast by a huge array of aircraft over Buckingham Palace. She will also host President Donald Trump at Windsor Castle on Friday.

Royal Ascot - Day Four - Ascot Racecourse
Queen Elizabeth
| Credit: Steve Parsons/PA Images/Getty Images

The Queen is traveling back from Sandringham, Norfolk, where she spent the weekend, a source confirms. And palace sources say there is no cause for any concern about the health of either her or Philip, 97, who has retired from public duties but appeared at the wedding of their grandson Prince Harry and has been alongside the Queen at two polo matches last month.

Everyone in the family is “comfortable with the arrangement,” the source adds.

On June 28, the Queen canceled an outing after complaining of feeling sick. The 92-year-old was set to attend a special church service to mark the bicentenary of an order of chivalry but was feeling “under the weather,” a Buckingham Palace spokeswoman said.

Those attending at The Chapel Royal in St. James’s Palace, include Harry, 33, and Meghan Markle, 36, and Prince Charles, 69, and Camilla, Duchess of Cornwall, 70, and Kate’s parents Michael and Carole and her siblings James and Pippa.

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After the service, William and Kate, both 36, are hosting a tea party in Clarence House – and serving up more of their wedding cake. The cake was saved since their 2011 ceremony, and there is still enough to go around, despite it being used for the parties at the christenings of both Prince George and Princess Charlotte.

Meanwhile, the Archbishop of Canterbury, Justin Welby, tweeted that he was honored to be conducting the service.

“I’m delighted and privileged to be christening Prince Louis today – a precious child made in God’s image, just as we all are. Please join me in praying for him and his family on this special day,” he said.