Britain's Prince Philip, the husband of Queen Elizabeth II, was moved from one London hospital to another on Monday for treatment of an infection and observation of a preexisting heart condition, Buckingham Palace announced.

The 99-year-old Duke of Edinburgh was admitted to the King Edward VII Hospital in London on February 17 after feeling unwell. The palace later confirmed that he was being treated for an infection.

Philip spent 14 days and 13 nights there -- his longest stay in a hospital to date -- before he was transferred on Monday to St. Bartholomew's Hospital, also in London, where doctors will continue to treat him for an infection, as well as undertake testing and observation for a preexisting heart condition.

The Duke remains comfortable and is responding to treatment but is expected to remain in hospital until at least the end of the week, according to a statement from the royal communications office. 

Prince Philip's youngest son, Prince Edward, told the UK's Sky News recently that his father was doing "a lot better" and was looking forward to returning home.

"We've had some brilliant and lovely messages from all sorts of people. And we really appreciate that and so does he. I've been passing them on," Edward said. Philip's grandson, Prince William, previously said his grandfather was doing "ok" and that hospital staff were keeping an eye on him.

Prince Philip, who turns 100 in June, stepped back from public life in 2017 and has been taken to the hospital several times in recent years.

In December 2019, he received hospital treatment for a pre-existing condition.

The Duke of Edinburgh also surrendered his driving license in February 2019 after he was involved in a car crash.

The Queen and her husband have spent most of the past year at Windsor Castle, outside London, having moved away from Buckingham Palace during the first wave of the Covid-19 pandemic in spring 2020.

In April 2020, the Duke of Edinburgh made a rare public statement, thanking key workers across the UK. 

The Queen and Prince Philip both received the first dose of a Covid-19 vaccine in January 2021