The 91-year-old Duke of Edinburgh was admitted to the private London Clinic on Thursday evening for what Buckingham Palace said was a planned operation under general anaesthetic.
It was business as usual however for the 87-year-old queen, who went ahead with a visit on Friday to the BBC’s new headquarters just a few streets away from where her husband was being treated.
It is the fourth time in two years that Prince Philip has been hospitalised and follows “an abdominal investigation that took place last week”, a palace spokeswoman said.
The duke, who has been married to the queen for 65 years, is expected to stay in hospital for up to two weeks.
The spokeswoman insisted however that Prince Philip was “in good health” and said he had walked into the clinic “unaided” after being driven there.
Although he missed an event on Monday, the duke undertook a full diary of engagements this week and appeared in good spirits as he attended a Buckingham Palace garden party just hours before going into hospital.
He had been due to join the queen as she formally opened the BBC’s refurbished headquarters at New Broadcasting House on Friday morning, but she went ahead without him.
As she toured the building, John Humphrys, one of the BBC’s top presenters, asked how Prince Philip was. She replied: “I don’t know”.
The broadcaster said he looked well at the palace garden party and the monarch stated: “That’s because he’s not ill”.
BBC Director-General Tony Hall said he was sorry the duke was absent “and we wish him, all of us wish him, a speedy recovery”.
Palace officials gave no details about Prince Philip’s surgery but it could involve either keyhole surgery or more serious open surgery designed to look for abnormalities.
Before his admittance to hospital, the duke was pictured smiling in top hat and tails and chatting animatedly to some of the 8,000 guests at the garden party.
Guest John Peace, the lord-lieutenant of Nottinghamshire — the monarch’s representative in that county — said Prince Philip had been “telling jokes” and accompanying the queen, adding: “It was wonderful to see the Duke of Edinburgh with her.”
With the exception of sporting-related injuries, the duke has enjoyed good health, but there are signs that age is finally catching up with him as he approaches his 92nd birthday on Monday.
Two months earlier, a similar complaint saw him hospitalised for five nights in London, causing him to miss the last event of the queen’s diamond jubilee celebrations.
In December 2011, he was rushed to hospital with chest pains. He suffered a blocked coronary artery and required surgery, spending four nights — including Christmas Day — in hospital.
Prince Philip pulled out of a gala charity reception with the queen on Monday after temporarily losing his voice.
But he was back by her side the following day for a service at London’s Westminster Abbey marking the 60th anniversary of her coronation.
Prime Minister David Cameron offered the duke the country’s good wishes.
“The Duke of Edinburgh is held in the highest esteem by people right across our country,” he said.
“He’s an extraordinarily dedicated public servant and such an enormous support for our sovereign, that I know the whole country will be thinking about him, thinking about the family and wishing him well.”
The couple married in 1947, making Prince Philip the longest-serving royal consort in British history. The queen once described him as “my strength and stay all these years”.
They both maintain a busy schedule and although the queen has cut back her long-haul flights this year, the duke paid a private working visit to Canada in April.