The one strict baby-naming rule Prince Harry and Meghan Markle must follow.

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For most expectant parents, choosing a baby name can be a simultaneously exciting and stressful event.

It can involve pages and pages of scribbled out and scrunched up lists, nights spent poring over name meaning books, and sometimes taking a long look down the family tree for a name that holds tradition.

And, of course, you both have to agree on it. (Which might mean a tiny argument here and there).

Then, for some parents, there comes the secret-keeping. For anyone who’s friend or relative has given birth (or has done so themselves), there’s usually a guessing game involved while the soon-to-be parents remain tight-lipped and smug – waiting until the day their child is born to utter their name aloud.

Well, while Prince Harry and Meghan Markle’s name-choosing task may prove a little more lenient than royals before them, considering their distance in the line from the throne, there’s one rule they must abide by.

And it means they won’t be partaking in the secret-keeping games of parents before them.

Their chosen name must be approved by the Queen.

While there have been murmurs of an a unspoken rule that those in line for the throne must name their children after past kings or other royal ancestors, those not in direct succession have much more freedom – which means Harry and Meghan don’t necessarily have to choose a traditional name (even though they probably will).

“The further down the line of succession, the more likely you are to have a more unique or untraditional name,” Carolyn Harris, author of Raising Royalty: 1,000 Years of Royal Parenting, told Vogue Australia.

“We see, from the diversity of names among the Queen’s descendants, that the Queen does seem willing to allow the descendants to choose their own names.”

An example being Sarah Ferguson and Prince Andrew, who chose Beatrice and Eugenie for their daughters – names that weren’t considered traditional at all at the time.

Yes. They are the *edgy* royal names.

However, according to royal commentator Victoria Arbiter, Queen Elizabeth must know the name before it is released publicly to ensure it is “suitable”.

“Royals, however, also have to consider the great responsibility in naming a new member of the family and I expect they want to be a hundred per cent certain of their choice before announcing the name and sealing the baby’s place in history,”  Arbiter told Town and Country.

So while they do have some freedom… they also… don’t.

According to UK bookies, the hot favourites are bound to please The Queen. They’re tipping Victoria, Arthur, Albert, Diana, Elizabeth and Philip – all names with strong links to the family.