Prince Philip, the longest-serving royal consort in British history and a constant presence at Queen Elizabeth II's side for decades, died Friday aged 99, Buckingham Palace announced. He served 69 years supporting the Queen and retired from the royal service in 2017.

The death of the Duke of Edinburgh is a profound loss for the 94-year-old monarch, who once described him as her "strength and stay all these years".

"It is with deep sorrow that Her Majesty The Queen has announced the death of her beloved husband, His Royal Highness The Prince Philip, Duke of Edinburgh. His Royal Highness passed away peacefully this morning at Windsor Castle," the statement said.

Queen Elizabeth announced his passing “with deep sorrow” after he died peacefully in the morning at Windsor Castle, west of London, the palace said in a statement.

“The Royal Family join with people around the world in mourning his loss,” the statement said.

The outspoken former Navy commander devoted much of his life as the Queen’s husband to charity work — but was notorious for numerous gaffes, some of them causing offence.

He was admitted to hospital on February 16, and went home after a month during which he was treated for a pre-existing heart condition and an infection.

In tribute to the duke, Westminster Abbey began tolling its tenor bell once every 60 seconds at 18:00 BST. It rang out 99 times to honour each year of his life.

Earlier, the flag at Buckingham Palace was lowered to half-mast and a notice was posted on the gates to mark the duke's death.

People placed floral tributes outside the palace, while hundreds visited Windsor Castle to pay their respects.

However, the government urged the public not to gather or leave tributes at royal residences amid the coronavirus pandemic.