Prince Philip has been moved to a different hospital in London as part of his continuing treatment for an infection.
The Duke of Edinburgh, who celebrated his 99th birthday last June, has been taken from King Edward VII's hospital to St Bartholomew's Hospital, where he will undergo "testing and observation for a pre-existing heart condition".
Earlier this morning, an individual was seen leaving a side entrance of King Edward VII's Hospital, but was shielded from public view as they got into an ambulance.
In a statement, Buckingham Palace said: "The Duke of Edinburgh was today transferred from King Edward VII's Hospital to St Bartholomew's Hospital where doctors will continue to treat him for an infection, as well as undertake testing and observation for a pre-existing heart condition.
"The Duke remains comfortable and is responding to treatment but is expected to remain in hospital until at least the end of the week."
Prince Philip has been spending the latest lockdown with the Queen at Windsor Castle after they decided to have a quiet Christmas and remain at their Berkshire residence rather than have a family gathering at Sandringham.
Last month, he gave his approval to a motto adopted by HMS Magpie, one of the Royal Navy's smallest ships.
The Duke has had a life-long connection to the British military, including serving in the Second World War with the Royal Navy and being present in Tokyo Bay when Japan surrendered.
In 2020, he handed over his role as Colonel-in-Chief of The Rifles to the Duchess of Cornwall during a rare public appearance.