The Duke of Edinburgh was admitted to hospital last night as “a precautionary measure”, Buckingham Palace has said, the BBC reports.
He is being treated at the King Edward VII Hospital, London, for an infection arising from a pre-existing condition.
The Duke, 96, said in May that he would retire from royal duties this autumn, a move supported by the Queen.
She is still carrying out her official engagements and on Wednesday is delivering the Queen’s Speech to Parliament.
It sets out the government’s legislative programme, this time covering a two-year period and dominated by laws about Brexit.
In a statement on Tuesday morning, Buckingham Palace said the Prince of Wales would instead accompany the Queen to Parliament and Prince Philip was “disappointed” to miss it.
“Her Majesty is being kept informed and will attend Royal Ascot as planned this afternoon,” the palace said.