Prince Louis would have had a different name and royal title if it weren't for the Queen's intervention

Prince Louis celebrates his fourth birthday today, but his title would have been very different if it weren't for a rule change made by the Queen.

• Prince Louis was born on April 23, 2018, two days after his great-grandmother the Queen's birthday.
• Without his grandmother's input following a rule her father, King George VI made, his title would be very different.
• This follows royal news that The Queen was spotted being driven to check up on her beloved horses at Sandringham estate.

Kate and William's cute joke about Prince Louis shows just how adored he is. As the youngest of the three Cambridge children celebrates his fourth birthday, it's been revealed that without a change of rule by the Queen, his royal title would be very different.

Louis' official title is His Royal Highness Prince Louis of Cambridge, but this was only made possible thanks to his great-grandmother, the Queen.

Back in 1917, Her Majesty’s grandfather, King George VI, set out rules on which royals were eligible for titles - and who was too far down the line of succession to qualify for one.

His rule dictated that all of the sovereign's children would automatically become a Prince or Princess, as well as any grandchildren who are born through the male line.

However, the royal rules regarding Prince and Princess titles did not apply to great-grandchildren of the monarch, meaning Louis would not qualify as a Prince.

However, before the birth of William and Kate’s first child in 2013, the Queen made a number of changes to these rules.

Her Majesty’s changes meant that all children of the eldest child of the Prince of Wales, the title currently held by Prince Charles, would have Prince and Princess titles.

This meant when George was born, he was given the title His Royal Highness Prince George of Cambridge.

But although George is an heir to the throne, the rule also applied to his younger siblings, Charlotte and Louis.

So if the Queen had not made this change, Louis would not have been a Prince. Instead, he would have been known as Master Louis Cambridge, after his father’s title, or Master Louis Windsor after the House of Windsor.

This comes after it was revealed that Prince Louis is sharing his special day with his brother, Prince George. Not only is April 23rd the day that Prince Louis was born, but it’s also St George’s Day.

St George’s Day honors St George, the Patron Saint of England and eight-year-old Prince George shares his traditional name. Patron Saint days are often marked by the Royal Family and over the years they've shared sweet tributes online for each of the Home Nations’ Patron Saints.