The Duke of Edinburgh retired from public life last August, although he has appeared alongside the Queen at several events.
The duke's hip problem forced him to miss the annual Maundy Service with the Queen last week which this year was staged at Windsor Castle's St George's Chapel.
On Tuesday, Buckingham Palace announced that Prince Philip is in the hospital.
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However, his health has been an ongoing issue since previous year, when he was admitted to hospital in June for an infection. It said the hospital admission and surgery were planned. In March, he missed Prince Andrew's appointment as Colonel of Grenadier Guards, where he would have ceremonially handed over the role.
He has attended a total of 22,219 solo engagements since 1952 and has given up some special causes that are very close to his heart.
Officially, Queen Elizabeth has supported Prince Philip's decision to retire.
Philip, who turns 97 in June, was hoping to join the monarch at the same venue where Prince Harry and Meghan Markle will hold their wedding next month. Philip, who at the time had Greek and Danish royal titles, abandoned his previous titles to marry the future Queen.
The royal couple were married on November 20, 1947 when they were still Princess Elizabeth and Lieutenant Philip Mountbatten, at Westminster Abbey.