The Duke of Edinburgh has been admitted to hospital in London as "a precautionary measure".
Prince Philip, who celebrated his 99th birthday in June 2020, was taken to King Edward VII's Hospital in London on Tuesday evening after "feeling unwell".
Buckingham Palace says he has been admitted to hospital on the advice of his doctor and is expected to remain there "for a few days of observation and rest".
A spokesman for Prime Minister Boris Johnson said: "The PM sends his best wishes to the Duke of Edinburgh as he undergoes a few days of rest in hospital."
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.
The Duke received a coronavirus jab in January.
Also last month, he gave his approval to a motto adopted by HMS Magpie, one of the Royal Navy's smallest ships.
Last year, he handed over his role as Colonel-in-Chief of The Rifles to the Duchess of Cornwall during a rare public appearance.
Cover image: PA.