The Queen had a big say in the Cambridge's children's names

She is the Queen!

Prince Louis celebrates his fourth birthday today, but it turns out all the Duke and Duchess of Cambridge's children could have had very different names if it wasn't for the Queen.

Prince Louis' full name is officially His royal Highness Prince Louis of Cambridge, but he could have been known as Master Louis Cambridge or Master Louis Windsor instead.

Back in 1917 the Queen's grandfather King George V put in place a guidance for future members of the royal family to follow, and it dictated which royals were allowed to have titles.

The guide meant anyone who was quite far down in the line of succession would not receive a title.

While all the sovereign's children would take the Prince or Princess moniker, as well as grandchildren from the male bloodline, but it was not extended to great-grandchildren.

However, the 96-year-old royal changed that ruling when Kate Middleton and Prince William's first child, Prince George, was born.

Her Majesty extended this further to reach all of the Cambridge's children, including Princess Charlotte and Prince Louis, though it is deemed unlikely they will take the throne.

However, there are some further confusions with names and titles.

Princess Charlotte will not take on the Duchess title like her mother, unless she marries a Duke. She won’t automatically receive the title, as it is royal tradition that it is only given to male descendants.

But the little royal may be given another title when William becomes King. Charlotte could become the Princess Royal, currently the title of the Queen’s daughter, Princess Anne. It is usually given to the monarch’s eldest daughter, and as the Queen’s only daughter it was automatically passed to her.

Charlotte is also the only daughter of Prince William and Kate Middleton, making it likely that she will one day become the Princess Royal.

Whereas, Prince George and Prince Louis are likely to receive dukedoms when they are older, and George may also inherit his father’s title, Duke of Cambridge, when Prince William takes the throne.