For many years the duchess has kept the large scar concealed, however a few years ago fans noticed the distinctive mark beneath her hairline.
Speculation ranged, with some royal watchers convinced the scar was actually hair extensions, whilst others went as far as to wonder if she had undergone emergency surgery to have a tumour removed.
To put the fears of royal watchers to bed, Buckingham Palace released a statement where they said: “The scar is related to a childhood operation.”
Senior royal sources claimed the operation had been very serious.
Now an expert surgeon has suggested the scar is likely to be left over from a birthmark.
John Scurr, a consultant surgeon at the Lister Hospital in London told the Daily Mail: “I really doubt it was any serious medical condition.
“I would say it is as a result of an arteriovenous malformation – a birthmark – being removed.”