Catherine, Duchess of Cambridge, visits Downton Abbey's London set

Downton Abbeyhas welcomed a royal visitor and the TV show's creator has told the Duchess of Cambridge she's partly responsible for its global success.

Catherine, Duchess of Cambridge the royal more commonly called Kate visited the set of the award-winning costume drama at London's Ealing Studios on Thursday, meeting cast members including Jim Carter, who plays butler Mr. Carson, andMichelle Dockery, who plays Lady Mary Crawley.

Kate, who is expecting the birth of her second child withPrince William in April,visited the show's hair and makeup departments, toured scenery construction and watched a scene being filmed.

In the show's kitchen set,Kate received a chocolate cake from Downton's cooks Mrs. Patmore (Lesley Nicol) and Daisy (Sophie McShera).

Maggie Smith, the 80-year-old actress who plays the haughty and formidable matriarchthe dowager Countess ofGrantham,reportedly missed the duchess's visit.

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The Emmy and Golden Globe Award-winning period piece, thatfollows the lives and loves of the Crawley family and its servants in their stately Georgian country house, is one of the most popular shows to come out of Britain.

The show's writer, Julian Fellowes, described how a 2011 visit to the U.S. by Kate and her husband, Prince William, came as producers tried to raise the profile of the show.

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Fellowes said when the duchess mentioned she was a fan "this went into the media like an Exocet missile. And soon all of America and most of the world knew it."