The King was joined by some of his closest friends and family members for his private birthday dinner at Clarence House.
Pictured leaving Charles’s London residence on Tuesday evening were the Prince and Princess of Wales, Princess Beatrice and Zara and Mike Tindall, who all put on a glamorous display.
Kate looked stunning, donning a glittering emerald Needle and Thread gown, while William looked suave in a tuxedo.
The King’s niece Zara looked gorgeous in black LBD with glittering pearl accents, which she wore for the relaunch of Rebecca Vallance in Harrods earlier in the day.
She held hands with husband and former rugby star Mike as they left the royal residence.
Meanwhile, Princess Beatrice appeared to be wearing a velvet number as she waved from behind the wheel of her car. She did not appear to be joined by husband, Edoardo Mapelli Mozzi, who turns 40 later this week.
Beatrice’s mother, Sarah, Duchess of York did not appear to be among the guests, but she shared an image of King Charles on Instagram to wish him Happy Birthday.
It’s unlikely that Charles’s siblings attended the event, given the fact that they had evening engagements elsewhere.
The Duke of Edinburgh was at a reception for the Commonwealth Games Federation at Swissȏtel the Stamford in Singapore, while his wife, the Duchess of Edinburgh attended a dinner at Rochester Cathedral as patron of the Rochester Cathedral Trust.
The Princess Royal carried out engagements in Glasgow on Tuesday and was among the guests at Interfaith Glasgow’s Scottish Interfaith Week Forum at Glasgow City Chambers.
The King was joined by his maternal cousins, David Armstrong-Jones, 2nd Earl of Snowdon and Lady Sarah Chatto – the children of the late Princess Margaret and Antony Armstrong-Jones.
Charles has remained close to his cousins over the years and they have attended major royal events, including his coronation at Westminster Abbey in May.
The King marked his milestone 75th birthday by launching an initiative to support charities feeding the nation with unwanted food – and surprised a Big Issue seller with a generous donation.