The 96-year-old, who retired from his royal duties last year, checked in to King Edward VII Hospital in London yesterday, for hip surgery. "Further updates will be issued when appropriate", the palace said in a statement.

The prince announced in May that he was retiring from most public duties after decades of royal service.

He has been reported to be hobbled by hip pain, but the news of the planned surgery took many by surprise.

When his spouse Elizabeth was elevated as the monarch in 1952, Philip left the military service and was appointed as the Duke of Edinburgh - a charge which he he continued to assume till May 2017.

When it was announced previous 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. He was also hospitalized for an "infection stemming from a pre-existing condition" in June of previous year. He will undergo planned surgery on his hip on Tuesday.

Queen Elizabeth paid tribute to her husband in November 1997 during their Golden Wedding Celebrations.

Prince Philip has spent much of his life in good health, but was treated for a blocked coronary artery in 2011 and a bladder infection in 2012.

Aged just 18 months, he and his family were evacuated in a British Royal Navy ship from politically unstable Greece, with the toddler reputedly carried in a cot made from an orange box.

The couple had four children together, Prince Charles, Princess Anne, Prince Andrew, and Prince Edward.