Royals: Queen, Kate, Camilla step out together

Royals outside Fortnum and Mason
Britain's Queen Elizabeth II, right, Camilla, Duchess of Cornwall, centre, and Kate, Duchess of Cambridge stand outside the Fortnum and Mason department store for a ceremony to unveil a plaque to commemorate the regeneration of Piccadilly in central London, Thursday, March, 1, 2012.
AP Photo/Alastair Grant

(CBS News) In London, Queen Elizabeth II, Catherine, Duchess of Cambridge, and Prince Charles's wife Camilla, Duchess of Cornwall, made a rare joint appearance Thursday morning.

Catherine joined the queen and Camilla at the luxury department store Fortnum and Mason. To the royal family, it's kind of their corner shop.

The event is part of the queen's ongoing Diamond Jubilee celebrations that mark her 60 years on the throne. The store will send tea and biscuits to British troops serving in Afghanistan who won't be able to join in the celebrations back home.

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The brief visit is also something of a small-scale warm-up for Catherine, who will join the queen and husband Prince Phillip at a much larger affair next week.

It's the first time Catherine -- or Kate -- has accompanied the queen at an official engagement without her husband, Prince William by her side.

The prince is busy at his day job. He's currently on a tour of duty as a search-and-rescue pilot in the Falkland Islands off the coast of Argentina.

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Kate's been flying solo ever since he left one month ago, comfortably stepping into the spotlight to continue her royal duties.

But the queen rarely shares the stage, which makes Thursday's appearance something special. It's seen as a tacit royal seal of approval -- that the queen is comfortable with Catherine taking on a bigger role in representing the brand.

Her Majesty was normally only seen with Princess Diana at big events.

A royal adviser told CBS News that the royals often don't show up at public appearances together because they want to "spread the love."

Watch Charlie D'Agata's full report in the video above.