Queen Elizabeth and Prince Philip
Britain's Queen Elizabeth and Prince Philip are driven past well-wishers during celebrations for the Queen's 90th birthday, in Windsor, Britain April 21, 2016. Reuters/Toby Melville

Queen Elizabeth II and Prince Philip have been married for almost 69 years but never have they been seen showing public display of affection with each other. There’s a reason the Duke of Edinburgh, who is turning 95 on Friday, does not hold his wife’s hand in public.

The royal couple’s union has been unshakeable from the start. Even back when the public thought then-Princess Elizabeth was too good for the former Prince Philip of Greece and Denmark, their love prevailed. They married in 1947 and produced four children.

However, apart from offering a courteous hand to the Queen when they are walking, the Prince does not hold his Queen’s hands in public.

Queen Elizabeth and Prince Philip
Britain's Queen Elizabeth and Prince Philip proceed through the Royal Gallery as they leave after the State Opening of Parliament in the House of Lords, at the Palace of Westminster in London, Britain May 18, 2016. Reuters/Toby Melville

This does not mean Philip is embarrassed to be with the ruler of England. It’s just that the Queen’s consort sports traditional “stoic values.”

Royal biographer Gyles Brandreth told the Radio Times (via People) that Philip does not hold his wife’s hand in public because he is more of a “pragmatist.” His son, Prince Charles, on the other hand, is more of a “romantic.”

“I once asked Prince Philip about the reported differences between him and his eldest son, Prince Charles,” Brandreth wrote. “He acknowledged ‘one great difference’ between them. ‘He’s a romantic,’ he said, ‘and I’m a pragmatist – that means we do see things differently.’ He paused before adding, with a shrug, ‘And because I don’t see things as a romantic would, I’m unfeeling.’”

William and Kate PDA

The Queen and the Duke’s grandson, Prince William, also does not hold wife Kate Middleton’s hand while they are out on official royal function.

The Duke and Duchess of Cambridge have a different reason for that, though. The parents of Prince George and Princess Charlotte are often seen showing public display of affection, or PDA, in casual settings, but they rarely touch each other when they on an official engagement.

According to royal etiquette expert Myka Meier, there is no royal protocol against PDA. However, it’s more likely that William and Kate hold off on demonstrating their love in public because they are representing the Queen while they are working.

“The likely reasoning is more that while travelling on a tour such as the India trip, technically the couple are working representatives of British Monarchy,” she told People. “The couple are likely to show very little PDA, if any, to remain professional during their designated roles abroad.”

Read: Prince William appears emotional at Taj Mahal + Why he refrains to show PDA with Kate Middleton

Britain's Prince William, Duke of Cambridge and his wife Catherine, Duchess of Cambridge, trek up the mountain to the Paro Taktsang Monastery, Bhutan, April 15, 2016.
Britain's Prince William, Duke of Cambridge and his wife Catherine, Duchess of Cambridge, trek up the mountain to the Paro Taktsang Monastery, Bhutan, April 15, 2016. Reuters/Cathal McNaughton