Duchess of Cambridge
Catherine, Duchess of Cambridge, speaks to guests as she attends an event in support of the 'In Kind Direct' charity at Clarence House London Clarence House

Resplendent in a turquoise empire-line dress, Catherine, the Duchess of Cambridge, conducted her first solo engagement as a royal Wednesday, but also on display was a childhood secret: a three-inch scar on the left side of her temple.

A spokesman for the Duchess at St. James's Palace last night confirmed that the scar was the result of a surgery as a young child.

The scar related to a childhood operation, the Palace spokesman said, declining to divulge the kind of operation it was, as it is deemed a private matter.

Other senior royal sources confirmed it has been a very serious operation.

The Duchess' first solo appearance was in London, at a charity dinner for In Kind Direct at the Clarence House - a private dinner originally scheduled for her father-in-law, Prince Charles, who was unable to attend because of his tri[ to Riyadh to present condolences to the Saudi Royal Family following the death of the Crown Prince of Saudi Arabia.

The Duchess had a little bit of time beforehand to prepare for the engagement - it went very well, a Palace spokesperson said. She was so pleased that her first solo engagement was for the Prince of Wales, who has shown her so much support over the years.

The reception was held to thank funders and supports of the charity, which redistributes surplus good from manufacturers and retailers to UK charities. Prince Charles founded the charity in 1996.

Richard Boles, chief executive of In Kind Direct, said: This event was a unique opportunity for In Kind Direct to thank generous supporters who have helped us over the years to deliver so much benefit for UK charities and the millions of people they serve.

We were delighted that The Duchess was able to step in at such short notice after our founder was unexpectedly called away. The Duchess hosted a very special evening with absolute professionalism and charm.