The world's oldest and longest-reigning monarch spent the night in the hospital on Wednesday but returned to Windsor Castle the next day, with officials stating that she was in good spirits and back to work. The queen, who had to postpone a trip to Northern Ireland, was advised by her medical team to rest, but her illness was not related to COVID-19. The palace announced that she had some preliminary medical tests on Wednesday and returned to Windsor Castle on Thursday, still in good spirits. The reason for her medical attention was not disclosed, and some royal reporters hoped for a more detailed explanation. Prime Minister Boris Johnson sent his best wishes and mentioned that the queen was back at work. Johnson informed reporters that Her Majesty, Queen Elizabeth, has returned to work at her desk in Windsor after staying at the King Edward VII hospital in London for practical reasons. A source close to the queen mentioned that her medical team took a cautious approach and now she is resting and doing light official duties. Elizabeth, who is queen of multiple realms, including Australia and Canada, resumed work on Thursday afternoon and is carrying out some light duties. Despite significant political, social, and cultural changes during her reign, Elizabeth has symbolized stability for the British people, helping maintain the popularity of the monarchy. Her quiet and dutiful commitment to her responsibilities, even as she grows older, has earned her respect in Britain and beyond, including from those who wish to abolish the monarchy. Elizabeth recently hosted a drinks reception for billionaire business leaders at Windsor, following a green investment conference led by Prime Minister Boris Johnson. She was joined by her son Prince Charles and grandson Prince William, and they greeted guests like US climate envoy John Kerry without masks. The queen, wearing a teal outfit and pearls, appeared in photos smiling and chatting with guests, showcasing her good health as she approaches her 70th year on the throne. The last time she is believed to have stayed overnight in a hospital was in 2013 due to symptoms of gastroenteritis. In 2018, she had a successful surgery for an eye cataract, and in 2003, she underwent a knee operation. Royal officials are hesitant to discuss her health issues. Her husband, Prince Philip, passed away in April at the age of 99. Despite this, she continues to fulfill her official duties, though she has delegated more responsibilities to Charles and other members of the royal family due to her age. Recently, she was spotted using a walking stick in public for the first time, besides after her knee operation. She not only suffered the loss of her husband, whom she called her source of strength, but her second son Prince Andrew has also stepped back from royal responsibilities due to his association with Jeffrey Epstein. Additionally, her grandson Prince Harry and his wife Meghan have distanced themselves from the royal family and made critical remarks about Buckingham Palace after moving to Los Angeles. Queen Elizabeth's next important event is at the end of the month, where she will welcome world leaders at the start of COP26 in Glasgow.