The Duke of Edinburgh celebrates his 99th birthday with the release of an official photograph marking the milestone.

Philip and the Queen are pictured posing in the grounds of Windsor Castle in celebration of his June 10 birthday.

The photograph is the first public image of the duke since he was seen leaving a private hospital on Christmas Eve last year, following a four-night admission for treatment relating to an undisclosed but “pre-existing condition”.

And the picture, taken last week, says as much about Philip’s 72-year marriage to the head of state, who stands by her husband’s side, as his birthday.

Famously described by the Queen as her “strength and stay” the duke enters his 100th year in lockdown with the monarch, but is still active and engaging with events during the coronavirus outbreak.

Joe Little, managing editor of Majesty magazine, said about their time shielding together at Windsor Castle: “It’s an opportunity for them in their later years to reconnect… It is the perfect royal cocooning.”

He added: “They will make a fuss of him on Wednesday as much as you can make a fuss of the Duke of Edinburgh.”

In the birthday picture, taken in the castle’s quadrangle, the Queen wears a bright floral dress and the Cullinan V heart-shaped diamond brooch, while Philip, with his hands clasped behind his back, looks smart in a blazer, shirt and tie, and grey trousers.

The image follows the recent release of a photograph showing the Queen out riding in the grounds of Windsor Castle – with both pictures taken by PA news agency photographer Steve Parsons.

The duke is the longest serving consort in British history and also the oldest serving partner of a reigning monarch.

In a rare public message issued in April, Philip praised those tackling the coronavirus pandemic across the UK and keeping essential services running.

The comments, his first major statement since retiring in 2017, also recognised the “vital and urgent” medical and scientific work taking place.

Prince Philip of Greece and Denmark was born on the island of Corfu on June 10 1921 to Prince Andrew of Greece and Princess Alice of Battenberg.

His early years were marked by upheaval after the family went into exile following a military coup in Greece which overthrew Philip’s uncle, King Constantine I.

He moved to England to stay with relatives and study at Cheam Prep School in 1928, before spending a year at Salem School in south Germany, then finally enrolling at Gordonstoun School in Morayshire.

Philip went on to join the Royal Navy and, while a cadet, he caught the eye of a 13-year-old Princess Elizabeth.

He served with distinction during the Second World War and his friendship with the princess grew into love. They married two years after the end of the war.

Within five years, George VI had died and Princess Elizabeth had become Queen.