The Duke of Edinburgh is likely to stay in hospital over the weekend and into next week for rest and observation, Sky News understands.
It is also understood that Prince Philip remains in good spirits, and medics are acting out of an abundance of caution.
The Duke, 99, was admitted to the King Edward VII Hospital in London on Tuesday evening as a “precautionary measure” after feeling unwell.
A royal source said the issue was not coronavirus-related, that he was taken to hospital by car and not an ambulance, and he walked inside unaided.
The latest update on the Duke’s health comes after his grandson Prince Harry and wife Meghan announced they will not return to being working members of the Royal Family.
A Buckingham Palace statement said the royals were “saddened by their decision” but the couple “remain much loved members of the family”.
Prince Philip retired from public duties in 2017 and has been rarely seen since.
He last appeared in public in July 2020 when he transferred his role as colonel-in-chief of The Rifles to his daughter-in-law Camilla, Duchess of Cornwall.
He has been staying with the Queen at Windsor Castle since coronavirus restrictions were first introduced last year.
In his old age, the Duke has suffered a number of ailments, including being treated for a blocked coronary artery at Papworth Hospital in Cambridgeshire in December 2011.
He later received treatment for a bladder infection in June 2012, forcing him to miss the Queen’s Diamond Jubilee celebrations.
Exploratory surgery on his abdomen followed in June 2013 and he began to use hearing aids in 2014, aged 93.
He pulled out of a Battle of Jutland anniversary event in June 2016 citing a minor ailment which was followed soon after by his retirement in 2017.
Philip was involved in a car accident near the royal estate in Sandringham, Norfolk, in January 2019 but was unhurt and didn’t go to hospital.
He spent four nights at the King Edward Hospital in December 2019, where he was treated for a “pre-existing condition” before being discharged on Christmas Eve.
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