Prince Philip underwent a 'successful procedure' for his preexisting heart condition

• Prince Philip had a successful procedure for a preexisting heart condition, Buckingham Palace says.
• The Duke of Edinburgh was transferred to a specialist hospital for his condition on Monday.
• The 99-year-old has been hospitalized for 16 nights and will stay for "rest and recuperation."

Prince Philip had a "successful procedure" for his preexisting heart condition and is expected to remain in hospital for several days, Buckingham Palace said.

"Following The Duke of Edinburgh's successful procedure at St Bartholomew's Hospital on Wednesday, His Royal Highness has been transferred to King Edward VII's Hospital this morning. The Duke is expected to remain in hospital for continuing treatment for a number of days," a palace spokesperson said in a statement obtained by Insider on Friday.

The palace confirmed on Thursday that the duke underwent a procedure for a preexisting heart condition at St. Bartholomew's Hospital, a specialist cardiovascular hospital in London, where he had been transferred from King Edward VII's Hospital on Monday.

The Duke of Edinburgh was first admitted to King Edward VII's Hospital "for rest and observation" on February 16 after becoming unwell. The duke was able to walk in without assistance, and the visit was described as precautionary.

The palace later said he would stay in the hospital for longer than initially expected while he received treatment for an infection. The only publicly known visit Philip has received is from his son, Prince Charles.

In a statement obtained by Insider on Monday, it was confirmed that Philip was taken by ambulance to St. Bartholomew's Hospital, where he was expected to remain until the end of the week.

This 16-night stay is his longest hospitalization to date, but the BBC reports the Duchess of Cornwall has reassured people that Philip is "slightly improving."

During a visit to a vaccination center in Croydon, England, on Wednesday, Anne Sheehan, a receptionist at a general practice asked the duchess how her father-in-law was. Camilla replied: "We heard today that he's slightly improving. So, that's very good news. We'll keep our fingers crossed."

The duke is due to celebrate his 100th birthday in June.