London, UK - The UK's 99-year-old Prince Philip has returned to the private King Edward VII's Hospital in London after receiving treatment for an existing heart condition at a state-funded hospital elsewhere in the British capital.

The husband of Queen Elizabeth II "underwent a successful procedure for a pre-existing heart condition at St Bartholomew's Hospital in the City of London on Wednesday – just three months before his 100th birthday," Britain's Press Association (PA) reported on Friday.

The duke of Edinburgh was admitted to the private hospital on February 16 after he fell ill at Windsor Castle.

He was moved to St Bartholomew's on Monday for the heart procedure before being transferred back to King Edward VII's early on Friday, Buckingham Palace confirmed to PA.

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"The duke is expected to remain in hospital for continuing treatment for a number of days," the palace was cited by PA as saying.

On Tuesday, Camilla (73), the duchess of Cornwall and the wife of Philip's son, Prince Charles (72) , said this week that Philip was "slightly improving."

"We'll keep our fingers crossed," PA cited Camilla as saying.

His illness is not related to coronavirus. Queen Elizabeth II (94) and her husband both received their vaccinations in January.