The Duchess of Cambridge is still not fully recovered from the acute morning sickness that has blighted her third pregnancy but found herself playing the role of Dancing Queen today.
Kate, 35, was twirled around Platform 1 at Paddington station in London after making a surprise appearance alongside the Duke of Cambridge, Prince Harry and cast members from the new Paddington 2 movie at an event involving children from the charities they support.
She and an actor inside a Paddington costume danced to the sound of calypso band D-Lime, who play on the soundtrack of the first and second Paddington films.
It was Kate's second public appearance since Kensington Palace officially announced on September 4 that she was pregnant with her third child and suffering from the severe morning sickness hyperemesis gravidarum.
She has previously pulled out of engagements because of the HG, which can cause vomiting up to 60 times a day but decided to join her husband and brother-in-law as her condition has improved.
"She's feeling much better," William said.
An aide added: "The Duchess is feeling much better but she has still not fully recovered."
The three royals joined actor Hugh Bonneville and other members of the cast of Paddington 2 at the station, where they met 130 children from around a dozen of the 30 organisations supported by their royal charities forum.
They spent 45 minutes chatting to children on board the Belmond British Pullman steam train, the sister train to the Venice Simplon-Orient-Express, before waving them off on a journey into the English countryside.
Kate, in an AW13 Orla Kiely dress, which was £348 ($643) at the time of purchase, was blooming, bending down to speak at length to children and their parents.
She had a long chat with Esther Windsor and her daughter Lilly, 10, from the Anna Freud Centre in north London.
She discussed her shared love of art with Lilly. "So you're creative. It's great fun, isn't it?" she said. The two also discussed seeing the first Paddington movie and their plans to see the second, which opens on November 10.
Further along, Harry, 33, was kneeling on the floor to speak to children. "So I guess you guys are big Paddington Bear fans?" he asked. "Are you looking forward to seeing the second movie?"
Hugh Bonneville, who plays Henry Brown in the movie, praised the three royals for their support of children's charities.
He said: "Wherever they go awareness is brought to the causes they do wonderfully support. It's just fantastic when they can bring a bit of a spotlight to shine on these fantastic causes. Paddington is equally happy to smear them in marmalade!"
He said he didn't want to give too much away but revealed that the second movie's baddie, played by Hugh Grant, is "not quite so scary as Nicole Kidman" from the first one.
"It's been wonderful seeing all these kids so excited. This is a great way of launching the film," he added.
Today was the Duchess of Cambridge's second appearance since announcing she is expecting.
Last week, she revealed a tiny baby bump as she made her first public appearance since announcing her pregnancy last month.