All the times Prince Philip has made Kate Middleton giggle

The Duke of Edinburgh and the Duchess of Cambridge appear to have a sweet relationship, with Prince Philip always making his granddaughter-in-law laugh. Prince William and Kate were among the royals to send wishes to the Duke on his 99th birthday on Wednesday from their Norfolk home, Anmer Hall.

Before Prince Philip retired from public duties, aged 96, in August 2017, he was a regular fixture by the Queen's side at her engagements and formal events, such as Trooping the Colour. The Duke was among the royals to welcome Kate to the fold upon her marriage to William in 2011 and the pair have often been spotted having a good catch-up on the Buckingham Palace balcony. Take a look at their best moments together.

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The Duke and Duchess of Cambridge looked pleased to see the Duke of Edinburgh as they left St George's Chapel in Windsor after Princess Eugenie and Jack Brooksbank's wedding. Prince Philip has attended all of his grandchildren's nuptials to date.

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Kate and Philip looked deep in conversation as they walked to church with William in Sandringham, Norfolk in January 2018. The Duchess was pregnant with Prince Louis at the time.

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The 2017 Trooping the Colour was the last time the Duke appeared on the balcony during the parade to mark the Queen's official birthday. William and Kate were joined by their eldest children, Prince George and Princess Charlotte, and at one point, Prince Philip made the Duchess burst into giggles.

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The pair sat next to one another at the patron's lunch to celebrate the Queen's 90th birthday in 2016 and it looked like they had so much fun together!

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The Duchess beamed at the Duke as he turned to speak with her at the 2015 Trooping the Colour. It was one of Kate's first post-baby appearances after the birth of Princess Charlotte.

The Duke of Edinburgh has a close relationship with Princes William and Harry, but it's clear that he also adores his granddaughter-in-law Kate. The foursome were pictured together at Trooping the Colour in 2014.

The Duchess made her second appearance at Trooping the Colour in 2012, standing next to the Duke. 

Kate travelled to Leicester with the Queen and the Duke of Edinburgh on the royal train in 2012 and she seemed truly at ease with her in-laws. The trio were given a whistle-stop tour of the city together, with Kate telling one well-wisher that while she was missing William (who was posted to the Falkland Islands at the time), she said: "I'm being well looked after."