King Charles was joined by his royal cousin, David Armstrong-Jones, on Wednesday as the monarch marked the 35th anniversary of The King's Foundation in a star-studded event.
David, also known as the 2nd Earl of Snowdon is the oldest child of the monarch's aunt, Princess Margaret and her husband, Antony Armstrong-Jones. David was seen in a grey and black jacket and he smiled as he interacted with Sir Rod Stewart and his wife Penny Lancaster, who were named as celebrity ambassadors for the charity.
Another famous face at the event was gardener Alan Titchmarsh, who wore a grey suit as he interacted the monarch.
During the celebrations, which were hosted in Dumfries House, Charles was among those who placed items in a time capsule dedicated to the anniversary. The capsule will be opened in 100 years time and focus on what inspired people to devote their time to protecting the natural environment.
The King's Foundation was founded in 1990 aims to build sustainable communities and transform lives with a focus on the protection and promotion of nature. The charity's education programmes support 15,000 students every year.
Charles and cousin David have a close relationship, and the Earl of Snowdon is regularly seen at royal events including weddings, Royal Ascot, Trooping the Colour and the late Queen's Platinum Jubilee celebrations, as well as her state funeral.
The pair's close bond is seen in how David serves as the vice-president of The King's Foundation and deputises for the King for the charity whenever required.
Alongside his charity work, David is the founder of furniture company David Linley Furniture Ltd, which is now known simply as LINLEY. His occupation was supported by his artistic father and the Queen Mother, who would proudly display his work from when he was a child.
Speaking to Vanity Fair, he revealed: "It came around as the cigar box after lunch and it had Turkish cigarettes on one side and cigars on the other. I just thought it was such a lovely thing she did. She was actually not offering people cigars. She was showing my work in a very subtle way."
When David was born, he was fifth in line to the throne, however, he has since fallen to 25th; although he is the highest person on the list who is not descended from the late Queen.