The Duke of Edinburgh has been taken to hospital as a "precautionary measure", Buckingham Palace has said.
In a statement, the Palace said Prince Philip was admitted as a precautionary measure for treatment on an infection from a pre-existing condition.
He's said to be in good spirits and is disappointed to be missing Royal Ascot and the State Opening of Parliament.
His son, Prince Charles, will be accompanying Queen Elizabeth to the State Opening in his place.
"Her Majesty is being kept informed and will attend Royal Ascot as planned this afternoon," the statement said.
Earlier this year, Prince Philip announced he would be stepping down from public duties in the northern hemisphere's autumn.