London: Queen Elizabeth II`s husband Prince Philip underwent an exploratory operation on his abdomen on Friday, and was said to be making satisfactory progress in his recovery.
The Duke of Edinburgh, who turns 92 on Monday, 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 Queen Elizabeth, 87, 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.
The duke, who has been married to the queen for 65 years, is expected to stay in hospital for up to two weeks.
It is the fourth time in two years that Britain`s longest-serving royal consort has been hospitalised.
"The Duke of Edinburgh has had an exploratory operation following abdominal investigations," Buckingham Palace said in a brief statement.
"The results will now be analysed. At this early stage he is progressing satisfactorily.
"Further updates will continue to be issued when appropriate."
The abdominal investigations took place last week.
Prince Philip is otherwise "in good health" and had walked into the clinic "unaided" after being driven there, a palace spokeswoman said.
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 a palace garden party just before entering hospital 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".
Although he pulled out of a gala charity reception with the queen on Monday after temporarily losing his voice, the duke otherwise undertook a full diary of engagements this week.
He was back by her side the following day for a service at London`s Westminster Abbey marking the 60th anniversary of her coronation.
He also appeared in good spirits as he attended the Buckingham Palace garden party just hours before going into hospital.
He was pictured smiling in top hat and tails, chatting animatedly and sharing jokes with some of the 8,000 guests.
Peter Phillips, the duke`s eldest grandchild, said the family were being informed about his progress.
"Our thoughts and prayers are with him, we know that he`s in good hands and we`ve been kept up to date in terms of what`s happening," Princess Anne`s son told the BBC.
"But he`s one of those people who wouldn`t want you to stop just because he`s gone into hospital."
British 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."
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.
He decided to slow down his workload as he entered his 90s.
In August last year, he was admitted to hospital in Scotland with a bladder infection.
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.
Married since 1947, 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 working visit to Canada in April.