Britain's Duchess Catherine unveiled a scar on her head during her first official solo engagement.

The royal - who is married to Prince William - wore her hair back for a charity event in London yesterday (27.10.11), exposing a long scar, with St James' Palace confirming it is from surgery in childhood, but refused to say what for.

A representative said: "The scar related to a childhood operation."

John Scurr - consultant surgeon at the Lister hospital in London - said he believed it could be a scar from the removal of a birth mark.

He said: "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 is remarkable, given the measurement, that no-one has noticed before."

William also has a scar on his forehead as a result of a golfing accident at the age of 13.