Kate Middleton visited the set of Downton Abbey, ITV's award-winning costume drama, located at London's Ealing Studio. Upon her arrival, she was presented with a posy by four-year-old Zac Barker. She also met his identical twin brother, Oliver. The two child actors both Lady Mary's son, George.

Middleton met stars of the the popular television show including Jim Carter who plays butler Carson and Michelle Dockery who plays Lady Mary Crawley.

The duchess would not be drawn on who her favourite character of the series is when asked by actor Hugh Bonneville, who plays the Earl of Grantham, saying she had to be diplomatic.

The duchess visited hair and makeup departments, toured scenery construction and watched a scene being filmed.

Visiting the kitchen set, where she was greeted by actresses Lesley Nicol and Sophie McShera who play Mrs Patmore the cook and Daisy the kitchen maid, Middleton joked with them about their cooking skills.

Prince William's wife, who is eight months pregnant, wore an elegant dress from maternity brand Jojo Maman Bebe, which retails for £69. She completed the chic look with black heels and a matching black clutch bag. The duchess is due to give birth to her second child at the end of April.

Downton Abbey chronicles the lives of an aristocratic family and their servants at Highclere House, a Victorian castle used as the location for the drama series. But many of the drama's interior scenes are filmed at Ealing Studios in west London.

The show's writer, Julian Fellowes, described how a 2011 visit to the US by Middleton and her husband came as producers were trying to raise the profile of the show. 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".

Kate Middleton Downton Abbey
Julian Fellowes watches as the Duchess of Cambridge unveils a plaque commemorating her visit Chris Jackson/Getty Images

The sixth series of Downton Abbey has been commissioned and is currently in production.