Britain’s Prince Philip, the 99-year-old husband of Queen Elizabeth, underwent a successful procedure for a pre-existing heart condition on Wednesday, Buckingham Palace said in a statement on Thursday.

Philip was admitted to hospital on Feb. 16 after he felt unwell, to receive treatment for an unspecified, but not COVID-19-related, infection.

On Monday, he was transferred to a different hospital in central London, with the palace saying at the time that he would have heart tests and continue to be treated for the infection.

RELATED: Prince Philip Is ‘Slightly Improving,’ Duchess Camilla Says

“The Duke of Edinburgh yesterday underwent a successful procedure for a pre-existing heart condition at St Bartholomew’s Hospital,” the palace said, using Philip’s formal title.

“His Royal Highness will remain in hospital for treatment, rest and recuperation for a number of days,” the statement said.

The Palace then confirmed Friday, “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.”

Since being admitted to hospital on Feb. 16, the duke has been publicly visited only by his son and heir Prince Charles.

The queen, 94, has remained at Windsor Castle west of London, where the couple have been staying during the coronavirus pandemic, and last week continued to carry out her official duties by video.

RELATED: Prince Philip, 99, Moves To Different Hospital For Heart Tests

She and Philip have received their first COVID-19 vaccine dose.

Greek-born Philip, who turns 100 in June, has required hospital treatment several times in the last decade for a recurrence of a bladder infection.

At Christmas in 2011 he had an operation to clear a blocked artery in his heart after being rushed to hospital with chest pains.

Reporting by Andy Bruce and Estelle Shirbon, editing by William James.