LONDON — Buckingham Palace says Prince Philip has had a successful heart procedure in a London hospital.

The palace says the 99-year-old Duke of Edinburgh, the husband of Queen Elizabeth II, “underwent a successful procedure for a pre-existing heart condition at St Bartholomew’s Hospital.”

It said he is expected to remain in hospital for treatment, rest and recuperation for a number of days.”

Philip has been hospitalized since being admitted to King Edward VII’s Hospital in London on Feb. 16, where he was treated for an infection.

On Monday he was transferred to a specialized cardiac care hospital, St. Bartholomew’s.

Daughter-in-law Camilla, Duchess of Cornwall, said Wednesday that Philip’s condition was “slightly improving.”