Prince Philip and Queen Elizabeth II pose for picture for his 99th birthday

Prince Philip, the Duke of Edinburgh, posed for a photo with his wife Elizabeth II, the Queen of England, to mark his milestone entry into the 100th year of his life.

Prince Philip, who has been isolating with Queen Elizabeth II at Windsor Castle since the outbreak of novel coronavirus in the United Kingdom, is expected to have a quiet celebration for his 99th birthday on Wednesday. Buckingham Palace, the official residence of the British monarch and the Duke of Edinburgh, shared an adorable portrait of the happy couple a day ahead of the royal's birthday.

The picture shared by the Buckingham Palace on 'The Royal Family' social media accounts was taken earlier this month in the quadrangle at Windsor Castle in Berkshire, where the couple often retreats for holidays. The famous round tower of the palace could also be seen in the background of the picture.

Prince Philip sported a blazer, shirt, a Household Division tie, and grey trousers for the portrait, while the queen opted for a bright floral Angela Kelly Outfit paired with her signature pearl necklace and the Cullinan V diamond brooch.

According to reports, the Duke will not have a grand celebration or family gathering for his milestone birthday, though it is expected he will connect with the rest of the British royal family via video calls.

According to Daily Mail, a royal expert has claimed that the couple has spent more time under the same roof together during lockdown than they have in years. Since his retirement from royal duties at the age of 96, the duke spends most of his time at his cottage Wood Farm in Sandringham estate, more than 100 miles away from the queen who resides at Buckingham Palace.

"But it's an opportunity for them in their later years to reconnect. It is the perfect royal cocooning," said Joe Little, managing editor of Majesty magazine.

The queen, who celebrated her original birthday in isolation with Prince Philip on April 21, will also mark her official birthday later this week. As the annual Trooping the Colour celebrations and fly-past at Buckingham Palace stand cancelled in wake of the coronavirus pandemic, a mini-version of the parade will be performed by the Welsh Guards for the 94-year-old at the Windsor Castle.

Attendance of her children, grandchildren, and great-grandchildren at the event has not been confirmed yet. The monarch's official birthday is celebrated annually on the second Saturday of June.