It is not a good sign when Britain’s Queen Elizabeth II misses a planned public service.

But that is what she will do today, at London’s St. Paul’s Cathedral, because she is feeling unwell, Buckingham Palace said in a statement and CNN reported.

Maybe it’s nothing. Maybe it’s something.

The British monarch, after all, is 92 years old and has ruled the monarchy for 65 years. And at least one British publication has already noted this: “The shock announcement has left royal fans fearing for the queen’s health.”

She also had a busy schedule these last couple of weeks, including appearances at the Royal Ascot horse show last week.

She “rarely misses scheduled public events,” CNN noted. Yet she won’t be at Thursday’s service marking the 200th anniversary of the Order of St. Michael and St. George.

The Queen is “feeling under the weather today and has decided not to attend this morning’s service at St. Paul’s Cathedral,” the palace said in a statement.

Instead, “Her Majesty will be represented by the Duke of Kent as Grand Master of the Order.”

While millions of people around the globe cannot ever imagine a world without Queen Elizabeth, it will also surprise no one that meticulous plans have been in place for years, literally, should anything untoward happen to the head of the British monarchy.

Those plans would then unwind with clocklike precision — marking the passing of one monarch and the ascension of another.

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Related: 17 Things That Will Occur When Queen Elizabeth Dies

The Queen’s eldest son, Charles, Prince of Wales, is first in line for the throne after his mother’s passing. Charles would make his first address as head of state on the evening of his mother’s death, as The Guardian has noted.

The next morning, the flags would be raised and he would be proclaimed King of England.

Last year, in a fascinating piece, The Guardian explained the detailed, point-by-point series of actions that will occur when the sad day does arrive that the Queen passes from this Earth — which everyone sincerely hopes is far, far off in the distance.

(photo credit, homepage image: Her Majesty Queen Elizabeth II, CC BY 2.0, by Foreign and Commonwealth Office; photo credit, article image: Her Majesty the QueenCC BY 2.0, by Chatham House)