Queen Elizabeth II's 96-year-old husband Prince Philip successfully underwent hip surgery on Wednesday at a private hospital in London and is in "good spirits" recovering, Buckingham Palace said in a statement.
The Duke of Edinburgh has been admitted to King Edward VII's Hospital in Marylebone, central London, for the surgery.
It is understood that the operation will require a general anaesthetic.
Philip, or the Duke of Edinburgh as he is known in Britain, retired from public life last August.
Both the Duke of Edinburgh and the Queen had been staying at Windsor Castle. But in early March he was seen carriage driving at Windsor. Buckingham Palace has said it will provide updates "when appropriate" but has not provided details about the nature of the surgery. "That's more important than someone's chronological age".
A month later he was admitted to the King Edward VII Hospital as "a precautionary measure" following an infection arising from a pre-existing condition.
This evening's announcement confirms that The Queen's husband underwent a full hip replacement procedure.
When it was announced past year that he would be retiring from official engagements, Buckingham Palace stressed that the decision was not health-related and he had the full support of the Queen.
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He has carried out about 22,000 solo royal engagements since Elizabeth became Queen in 1952.
Prince Philip is in "good spirits" after having a hip replacement.
Also invited will be 200 people from various charities associated with the couple, 100 students from two local schools, 610 Windsor Castle community members and 530 Members of The Royal Households and Crown Estate.
Image: Prince Philip has had an artificial implant to replace one of his hips.
There will be physiotherapy exercises to do at home and crutches are needed for about four to six weeks.
It has not been revealed how long he will be in hospital and if he will miss any upcoming events this spring, most notably the wedding of his grandson Harry to former actress Meghan Markle on 19 May.
Patients tend to feel back to normal after about three months.