Instructions: Generate an appropriate single-sentence summary for the given text such that it includes the main topic of the text.
Input: Prince Philip, who celebrates his birthday on Wednesday, has been shielding with the Queen at Windsor Castle during the coronavirus lockdown. The photo was taken in the castle's grounds during sunny weather last week. It is the first public photo of the duke since he was seen leaving hospital in London on 24 December last year. Prince Philip spent four nights in the private King Edward VII's Hospital in relation to a "pre-existing condition". In the picture, which was taken by a Press Association photographer, the duke is wearing a Household Division tie. The Queen is wearing a heart-shaped 18.8 carat diamond brooch called Cullinan V, which she has worn many times, including for her granddaughter Princess Eugenie's wedding and London Fashion Week. It follows another photograph last week that showed the Queen, 94, riding a pony called Balmoral Fern in Windsor Home Park. Prince Philip, who has been married to the Queen for 72 years, has rarely been seen in public since he retired from royal duties in 2017. He is the longest-serving consort in British history and the oldest serving partner of a reigning monarch. The duke issued a rare statement in April thanking key workers who were keeping essential services running during the pandemic. It followed the Queen's own message on television, watched by about 24 million viewers. Meanwhile the Duke of Cambridge said he was worried about Prince Philip and the Queen during the coronavirus outbreak, but said his grandparents were doing everything they could to ensure they were protected and isolated. "Obviously I think very carefully about my grandparents who are the age they're at - we're doing everything we can to make sure that they're isolated away and protected from this," said Prince William. The Queen cut short her official duties because of the coronavirus in mid-March. Prince Philip, who had been staying at the Sandringham estate, was flown by helicopter to join the Queen at Windsor Castle. The government's rules for the lockdown identified groups of "clinically vulnerable" people who should take particular care to minimise contact with anyone outside their household. They included those aged 70 or over, "regardless of medical conditions". The managing editor of Majesty magazine, Joe Little, said the royal couple's time in lockdown together was "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."
Output:
Buckingham Palace has released a new photograph of the Queen and the Duke of Edinburgh to mark the duke's 99th birthday.