Prince Philip, the 91-year-old husband of Britain's Queen Elizabeth, was to undergo "exploratory'' surgery on his abdomen on Friday.
His wife of 65 years carried on with her official engagements, visiting the BBC just half a mile from the hospital where Philip's operation will take place.
Philip, who turns 92 next week, was admitted to the London Clinic on Thursday and is expected to remain there for two weeks after what Buckingham Palace described as "an exploratory operation following abdominal investigations''.
Royal aides said the surgery would be done on Friday. It will be fourth time Prince Philip, also known as the Duke of Edinburgh, has undergone hospital treatment since Christmas 2011.
Philip was admitted to the hospital during the queen's Diamond Jubilee last year with a bladder infection, putting a dampener on celebrations to mark the milestone.
The 87-year-old queen visited the BBC's newly-opened headquarters alone on Friday. She left without making public reference to Philip's hospital stay.
Philip was taken to the London Clinic by appointment after attending a garden party at Buckingham Palace with Queen Elizabeth. Television footage showed him in a grey top hat and tails, smiling and chatting with guests.
Married in 1947, Philip - the son of the exiled Prince Andrew of Greece - has proved a steadfast albeit sometimes controversial consort to the Queen, renowned in Britain for his outspoken comments and off-the-cuff remarks.
"I think he has done a fantastic job supporting the queen,'' said Margaret Stead, 66, near the clinic. "He's in the best hands at the London Clinic.''
Against a backdrop of trumpets and cheering crowds, the queen and Philip were recently joined by 2,000 guests at Westminster Abbey on Tuesday to celebrate 60 years since her coronation.
"My best wishes to the Duke of Edinburgh who is in hospital,'' Prime Minister David Cameron said on Twitter on Thursday evening. "I hope he has a swift recovery.''
Britain's Prince Philip is pictured Windsor, England April 30, 2013.
Britain's Queen Elizabeth sits with Prince Philip as she delivers her speech in the House of Lords, during the State Opening of Parliament, London, May 8, 2013.
Britain's Prince Philip leaves after the Commonwealth Day Observance at Westminster Abbey, London, March 11, 2013.
Britain's Prince Philip walks past Czech army veterans who fought for Great Britain during Word War II after he laid a wreath at the Memorial of Czech pilots in Prague, March 29, 1996.
The Duke of Edinburgh Prince Phillip meets a Tuatara, a unique New Zealand reptile, face to face at a WWF meeting in Wellington, Jan. 3, 1995.