United Kingdom, April 1 -- Prince Philip almost died "twice" after undergoing secret heart surgery in 2021, according to a new book.

Queen Elizabeth's late husband was taken ill in early 2021 and was admitted to a hospital in London for tests before being transferred to another medical centre to undergo an operation - and the doctors "nearly lost him twice".

Royal historian Hugo Vickers makes the claim in his new book Queen Elizabeth II, writing: "The Duke of Edinburgh, then aged 99, was admitted to the Edward VII Hospital in London for tests.

"On March 1, he was moved to St Bartholomew's Hospital, where he had an operation on his heart. His medical team nearly lost him twice."

Philip survived the scare but his health never recovered ...