Prince Harry has had a surprise 40th birthday message from his older brother

But William and his wife Catherine, Princess of Wales, 42, posted on Instagram: "Wishing a Happy 40th Birthday to The Duke of Sussex."

The Waleses' official account also included a photo of Harry smiling while wearing a grey suit and white shirt.

But the post was not signed off with William or Kate's initials, as is the tradition when royals personally write posts.

It came as King Charles, 75, also wished Harry a happy 40th on social media.

The monarch and his wife, Harry's stepmother Queen Camilla, 77, shared a message on their official Royal Family X account on Sunday to mark the Duke of Sussex's big day.

Their message said alongside a cake emoji: "Wishing The Duke of Sussex a very happy 40th birthday today!"

The post also included a photograph of a smiling Prince Harry.

It was a picture taken in 2018, during Harry's visit with his wife Meghan, Duchess of Sussex to the 'Digital Docklands' in Dublin.

Harry is set to celebrate his birthday privately in Montecito, California, with Meghan, 43, and their children Archie, five, and Lilibet, three.

A source told the Sunday Express about how Charles is set to call his youngest son: "The King will reach out to Harry on his birthday. Although the family are not as close as they once were, there is still a lot of love there.

"They tend to use Skype when they communicate because they can see each other and it's all set up by staff so it runs smoothly."