The husband of Britain's Queen Elizabeth II has been taken to hospital for treatment for a pre-existing condition, Buckingham Palace has said.
Prince Philip (98) travelled to the King Edward VII Hospital in London on Friday morning as a precautionary measure on advice of his doctor.
He was not taken by ambulance and it was a planned admission.
The palace announcement came as Queen Elizabeth II arrived at her Norfolk estate for her Christmas break, after carrying out the state of opening of parliament on Thursday.
The royal couple have been married for more than 70 years.
A Buckingham Palace statement said: "The Duke of Edinburgh travelled from Norfolk this morning to the King Edward VII Hospital in London for observation and treatment in relation to a pre-existing condition.
"The admission is a precautionary measure, on the advice of his royal highness' doctor."
He is expected to be in hospital for a few days.
Prince Philip has suffered ill health in recent years, most recently in 2018 when he was admitted to hospital for a planned operation on his hip.
In January this year, he was involved in a car crash when the Land Rover he was driving flipped over after colliding with another car.