London, UK - The UK's 99-year-old Prince Philip has left the hospital in London where he has been recovering after heart surgery.

The prince, who is married to Queen Elizabeth II, was first admitted to King Edward VII's Hospital in London on February 16 for treatment of an infection.

He was then moved to a new hospital in London, St Bartholomew's, where doctors performed testing and put him under observation for a pre-existing heart condition.

The prince, who is also known as the duke of Edinburgh, then returned to the King Edward VII's a few days later on March 5 and subsequently left the premises on Tuesday.

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He is returning to Windsor Castle, 20 miles west of London, where he and the Queen have been residing over the past few months, a Buckingham Palace statement said.

The prince is understood to be in good spirits.

"The Duke of Edinburgh has today been discharged from King Edward VII's Hospital and has returned to Windsor Castle, following treatment for an infection and a successful procedure for a pre-existing condition," the statement read.

"His Royal Highness wishes to thank all the medical staff who looked after him at both King Edward VII's Hospital and St Bartholomew's Hospital, and everyone who has sent their good wishes," the statement added.

Later on Tuesday, the senior member of the royal family was photographed sitting in the back of a car.