Britain's Prince Philip does not have COVID-19 and his admission to hospital on Tuesday evening was precautionary and not an emergency admission, a royal source said.
The palace says the husband of Queen Elizabeth II was admitted to the private King Edward VII Hospital on Tuesday evening.
A statement from Buckingham Palace said the prince was admitted on the advice of his doctor after feeling unwell.
It called the admission "a precautionary measure" taken on the advice of Philip's doctor.
The duke had been feeling unwell for a few days, but it was not related to coronavirus, the source added.
The prince and the Queen, 94, have been maintaining social distancing rules at Windsor Castle, because their age puts them at risk from Covid.
The Duke has been treated for various ailments in recent years, including a hip replacement and bladder infections.
The revelation caused shockwaves at the palace, amid confirmation that Winfrey could ask "anything she wants".
Philip is rarely seen in public after he stepped down from official engagements in August 2017.
"The Duke of Edinburgh traveled from Norfolk this morning to the King Edward VII hospital in London for observation and treatment in relation to a pre-existing condition", a rep for Buckingham Palace told Fox News in a statement at the time.
Prince Philip and Queen Elizabeth celebrated their 73rd anniversary last November.