Britain's Lady Gabriella Windsor's wedding

The Duke and Duchess of Sussex have wished Prince Philip a "very happy birthday" on Instagram. 

Prince Harry and Duchess Meghan have sent their well-wishes to Harry's grandfather on his 98th birthday, affectionately referring to the Duke of Edinburgh as "grandpa".

The couple - who became parents to their first son Archie last month - shared two photos of Philip, one of him besides Harry and another showing a younger version of the royal dancing with his wife, Queen Elizabeth II. 

They wrote: "Wishing His Royal Highness The Duke of Edinburgh, Sir, Grandpa a very Happy 98th Birthday!"

Their birthday message has been liked 400,000 times and royal fans have gushed over the pair's special post. 

One wrote: "Love, love the second picture! He makes the Queen so happy. Happy Birthday Prince Philip (sic)"

Another said: "A wonderful man! Happy birthday sir" 

A third commented: "Happy birthday and best wishes to His Royal Highness the Duke of Edinburgh! Long live the Prince. 98th is a blessing. (sic)"

Harry, 34, and Meghan, 37, weren't the only ones to celebrate the occasion with his brother Prince William and sister-in-law Duchess Catherine also sharing touching tribute on the Kensington Royal Instagram account that read: "Wishing a very Happy 98th Birthday to His Royal Highness The Duke of Edinburgh!"

The duke's granddaughter Princess Eugenie also posted a message online, writing: "Happy Birthday to HRH The Duke of Edinburgh.

"I found a couple of classic photographs of Grandpa and I on Christmas Day and Trooping the Colour a few years ago now."

The Royal Family's official Instagram account also shared a birthday message, posting photos of the senior royal at Lady Gabriella Windsor and Thomas Kingston's wedding this year and photographed in 1953 - 66 years ago.