The Duke of Edinburgh faces two weeks in hospital after undergoing an exploratory operation on his abdomen today.
Philip, who is 92 on Monday, was admitted to the London Clinic on Thursday following a garden party at Buckingham Palace.
A Buckingham Palace spokeswoman said the operation, which will be carried out under general anaesthetic, was a planned admission following investigations carried out over the past week, and emphasised that the Duke “is in very good health”.
The operation means that Philip will be unable to accompany the Queen as she officially opens the BBC’s new £1 billion home at Broadcasting House in central London today.
The spokeswoman could not confirm if the Queen or any other members of the Royal Family are due to visit him in the coming days.
The Duke pulled out of an official engagement at the palace on Monday after temporarily losing his voice, the Palace said, an illness not thought to be connected with today’s operation.
The Palace said in a statement last night: “His Royal Highness The Duke of Edinburgh has been admitted to the London Clinic for an exploratory operation following abdominal investigations. He is expected to stay in hospital for up to two weeks. Further updates will be issued when appropriate.”
The Queen and the Duke had appeared together on the steps of Buckingham Palace at 4pm on Thursday, when the National Anthem was played to mark the start of the garden party.
Despite the fierce sun, with temperatures at approximately 22C (72F), Philip appeared relaxed and happily chatted to guests as he walked around the garden, giving no indication of his imminent admission to hospital.
Lord-Lieutenant of Nottinghamshire Sir John Peace attended the garden party where he said the Duke had been “telling jokes” – but he would not divulge what they were about.
Speaking of meeting the Queen at the event, he said: “It was wonderful to see the Duke of Edinburgh with her.”
Other than Monday’s cancellation, the Duke carried out this week’s engagements as planned.