As always, the Duchess of Cambridge was chic and stylish in her perfectly fitted cream coat, teamed with simple black heels and a small clutch.
She kept her brunette locks loose and waved, rather than tying them back in a ponytail as she did during yesterday's official visit to Margate.
Kate, 33, was greeted by young cast member Zac Barker on her arrival at Ealing Studios, bending down to accept a bunch of purple and pink flowers from him.
She also shook hands with Downton Abbey creator Julian Fellowes, who will be taking Kate on a tour of the set, which will include watching a scene being filmed in the servants' quarters.
Kate is thought to be a big fan of the ITV drama.
Allen Leech, who plays Branson, told US TV host Andy Cohen that he met Prince William shortly after the birth of William and Kate's son George.
"He actually said, 'I'm a big fan of the show – only now that my wife's had a baby. Obviously he's now got a lot of downtime so Kate's said, 'I'm watching this and you're watching it with me.'"
Today is Kate's third public engagement this week.
On Monday she attended the Commonwealth Observance Day with Prince William at Westminster Abbey, and yesterday she visited the Turner Contemporary art gallery in Margate, Kent.
She is expected to give birth to her second child in April.
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