Venturing outside despite Storm Claudia’s torrential rain, the couple greeted hundreds who had waited for hours in hopes of seeing them. Crowds shouted “Happy Birthday!” and “Penblwydd Hapus, Your Majesty!” as the King accepted soft toys and handmade cards, while the Queen gathered several bouquets beneath her umbrella.

“Nice wet day!” Camilla joked as she shook hands with well-wishers.

Built in 1825, the 72-room Cyfartha Castle now serves as a museum and art gallery, home to more than 300 artworks — the largest collection outside the National Museum of Wales.

Elsewhere across the UK, ceremonial gun salutes rang out from Green Park, the Tower of London, and other national landmarks to honour the monarch’s birthday.

After nearly an hour at the castle, the King travelled to Taff’s Well near Cardiff to officially open the South Wales Metro Depot. There, he met Transport for Wales staff and toured the new facility built to service a fleet of 36 tram-trains. Charles even stepped into the driver’s seat of one of the modern vehicles.

Earlier in the day, Buckingham Palace released a new portrait of the King taken by photographer Millie Pilkington at Sandringham.
The birthday post read: “77 today! Thank you for the kind words and well wishes on His Majesty’s Birthday.”