Kate Middleton has a mysterious 3-inch scar on her head -- here's what experts believe happened

For Kate Middleton -- or any other member of the British royal family, for that matter -- no detail goes unnoticed. From the tiniest jewelry details to the not-so-subtle hack she uses to keep her updos in place, being a high-profile royal like the Duchess of Cambridge means subjecting yourself to constant scrutiny from the public.

And now, eagle-eyed royal fans have resurfaced yet another observation about the 37-year-old mother-of-three, and it's a detail that's (of course) been supplemented with its fair share of conspiracy theories.

Although it's not as apparent in newer photos, Duchess Kate has a three-inch scar on the left side of her head. You can see it peek through in this photo from her first-ever solo engagement, a 2011 event at Clarence House.

While the duchess has become skilled at concealing her scar under a hat or with an updo, many can't help but wonder where the scar originates from.

Initially, beauty fans suspected that it was just a protrusion from hair extensions, but a spokesman quickly refuted that suspicion. "The scar is related to a childhood operation," said the source to E! News in 2011. Of course, the spokesman's broad response only ignited concern from many: was it serious? Details, please!

Suspected a doctor to The Daily Mail at the time: "I really doubt it was any serious medical condition and I would say it is as a result of an arteriovenous malformation—a birthmark—being removed." It's "remarkable" that no one noticed it before the 2011 event given the size, said surgeon John Scurr to the publication.

Let's just go with that. And on that note, Kate's hairstylist definitely deserves a raise. Bravo!

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